This, from what I've seen, is both the best and worst thing you can ask about a story. Let me explain with a metaphor.
I knit. You can learn nifty obscure little techniques. For example, the choice of which yarn is held in front when doing colorwork can change the dominance of the color. You can use at least three different methods for adding stitches in the midst of working on something. My dad, however, tends to respond to a lot of the more esoteric stuff with the question, "But what do you do with it?" Usually, the answer is either that there's a slight aesthetic value, or - it's cool purely from the technical viewpoint. If it's cool purely from the technical point of view, then nine times out of ten, the average person doesn't care.
Moving back to writing now - why do I say this question is bad? Sometimes, you can run into people who have massive worlds with conlangs, elaborate societies, characters, but no plot. I hear from them, "I have this. I want to write it. But what do I do with it?" This also pops up in non-original fiction. I love this show / book / movie / whatever. I want to write something in that world. What do I do with it?
I think the problem often is that the world and the possibilities are so massive that there's hundreds of stories there. People may be afraid of not picking the 'right' story or they may want to show everything that they love in one story. Another possible fear is of changing the world too much or to the point of it not being the very thing that fascinates someone. A final, more difficult possibility is that the world is such a utopia that it's hard to find much to write about.
If you are stuck going 'what do I do?', I think there's two good tricks to try. One is pruning the world or looking at the world to find what you love most. The other is to look at how to throw a spanner into the works of the world.
(Before trying the stuff below, I'd suggest a list of people with all the 'important' information and a list of places with important details. That'll help you narrow down things that you have a lot of information about and things that are just background flavor. What, you ask, is important? That's up to you.)
Option one questions - (Pruning, narrowing focus, working with broad expanses.)
Can you limit your field of interest to one area or one time period? If so, what is relevant in this area or time period? What draws your interest to this area or time period? If not, why the broader scope?
Especially if you don't have a main character / set of primary characters, can you limit your cast to a smaller number of people that are your primary interest? If you don't have any characters at all, where could you find interesting people in this world? If there are no people (beings, whatever), what about visitors?
Working with your characters again, are they connected in some manner to events (present or future) that you want to focus on? Do they have a way to meet? If some of them are not connected right now, can you make them connected? Are they really another story?
Let's say you have a broad world / time period spanning frame of interest and a small cast. Can you make an excuse to explore the world or can you find interest in folowing someone's life over the relevant time periods? Does your characters want to travel? If not, would it be plausible to force them? If it's not logical for them to see all you want to show, find people who can see what you want, and find the story that fits your cast.
Let's say you have a broad frame of interest and a huge cast. If you cannot narrow your focus, try writing short snippets to see if any stand out to you as a place to narrow your focus. If that doesn't work, you may be best served by writing lots of short stories, perhaps covering the time period in question.
Option two - (I know who I want to write, but not what to write about them.)
Utopias are a commong problem when you don't know what to do with something. I hate utopias, personally. My reasons are mostly due to personal taste, but let's just say that they're usually implausible, poorly written, and most plots that would work in any other society feel forced. Many types of them are also cliche. If you have problems getting a plot in a utopian society, the traditional one is exploring the perfection or destroying it.
If your society or characters are static, you may have problems writing a plot. The best way to see if your place is static is to look at the history of your place or people. If you find a lot of 'this never changes', then a good way to disrupt this is to make something change. If Bob has never left Jamestown and his character is not solely interesting due to where he is, make him leave. If your peacefull village of Jamestown has never had anything happen to it, find out why or make something happen there.
Who's your character's enemies? What do they want or need? What do they love or like? What are they passionate about? If all the interesting stuff is in the past, write about that.
Burn something. What happens?
What kind of story do you want or like to write? What can you twist to make that kind of story happen? (You want porn? Then make your lovers and give them a fun place to get laid. Make excuses to have the porn be the focus.)
What if something in the past didn't happen?
Is something in your world really making plots hard? Can you remove it?
What would be unusual? Would it be fun to make this happen?
Name some neat historical events. Who could've seen it? Write something about them.
Look at what makes your characters interesting. If it's the place they are, then that's where you're interested. If you're interested in the people due to their connections to someone else, perhaps that's where your plot is. If you find that you can list a lot more nifty things about one person, that may be where you need to look for your plot.
Now, let's go back to the question again. How can it help you?
If you can't say what you can do with a facet of your world, then it's usually a good sign that you may have something that's true to your vision of the world but not relevant to the plot at this time. That means either your plot must change, or you simply will not spend a lot of words on the topic.
If you find yourself explaining in great detail what a facet of the world can do for believeablility, theme, plot, characters, etc., then you've found something that should be a major part of your story. If it isn't, ask why. A rule of thumb is that you want the good stuff to start coming as soon as possible. That doesn't mean you want the first chapter to be in media res with a crisis and wild flourishes of whatever and blatently more 'POW' than your second chapter. This does mean that you want the fascinating details of your world to show up in manageable bits as soon as possible. Don't spend hours explaining that this is pre-steam Medieval with horses, a king, coin based currency, and misogyny. Spend the words on things that make this place yours carefully so you're not drowning the readers in details, but you are using your ideas.
A slightly more tricky thing to look at is if your 'what does it do' item is serving a usefull function. Let's say you've got something strange in your story. Invisible knives used in dueling in strange maze like dungeons brightly lit by the crushed mushrooms on the floor, perhaps. Your readers need to be able to visualize this strangeness and it needs to be something that doesn't feel like it's odd for the sake of being odd. Why did this dueling start? What does it mean? Who watches it? Does the level of technology fit consistantly with the weird knives? Is anyone in your story going to ever hear about it? If not, can they use this detail to help an arguement, reinforce plot, be a historical detail for someone's life, etc? If not, what does this do for your world if no one's ever going to see the slightest hint of it? Do you have this amazingly vivid image that just isn't relevant? Give it a story. Don't weaken yours with this stronger thread.
Long pointless digression: I remember to this day a sci fi story where they described a world of emotionless telepaths, and the heroes escaped the city by using their frightening emotions. Frankly, the plot's left my memory. I remember a strange comment at the end of the story that a girl was told to encourage her brother to do 'italicized weird sounding word' to cool off. This action was snapping his fingers against his armpits, forming a sound. I assumed it was something like fanning himself, since whacking your armpits isn't too comfy. Nowhere in the story was there explanation of why fanning your armpits (while nude in a meadow, mind you) was supposed to make someone cool off. No one else complains of being too hot. No one mentions a desire to go off and fan their armpits. Now, if this was so internalized in their culture that it's second nature, there's no reason why the heroes wouldn't be doing it more. Even if it's that common, it's such a surreal image that it's hard for me, to this day, to see how it serves any purpose in the story save for 'here's futuristic people with odd customs flopped on grass and fanning their armpits.' It's not an organic part of the world.