I've talked about different pieces of building up a story. I've talked about the research, the character sketches, the world building. Now the question is, once you've gotten all this information, how the heck do you put it all together for a story?
The first thing you have to do is decide how much of that information you're going to use. You can have an entire novella/novel length book of world building, but is all of it really necessary for the story you're telling? Most likely not. You have to choose the most important items out of all of that work you did and find a way of putting them into the story. You might not have a purpose yet for that dissertation you wrote on the culture of a foreign country, but save it. You can use it in another story.
Characters. You've written these beautiful character sketches. If you're like me, they've got more information in them than you're likely to use. I tend to add a full background, a list of likes and dislikes, and maybe if I'm ambitious what their favorite foods/colors/etc. are. I don't do that lat one very often but I do tend to be very thorough in creating my character sketches.
Obviously, all that lovely information isn't going to make it into the book. If it does, you're probably going to bore your reader. So how do you decide which is the most important information? Think about how your story is going to go. Pinpoint the most important details that you can share in the story and make note of them. Those are the details you're going to use for your story.
Now, about that research you did. You've probably done a lot of reading and note taking on several different subjects. At least, you have if you're like me. You have all this lovely, useful information. The question again is how much are you going to use? That obscure culture you researched and referenced in your notes may be wonderful for a story some day but is it pertinent to the story you're working on now?
Once you've sorted your information out, then you can start writing your story. And even here you've got options. You can be a plotter - build yourself an outline, lay out precisely how your story is going to go, and work from that. Or you can do what I do - figure out the beginning and the end, and come up with a rough idea of some of the events you'd like to have in the story. And then just start writing and hope everything comes out all right in the end. Or you can avoid all of these steps and just start writing. Hey, it's all fixable in edits, right?