Leonard Balsera, one of the authors of Spirit of the Century, has written up a short and clear description of how to use FATE/SotC characters’ aspects in worldbuilding. If you’re just getting started in your FATE GMing career, give it a read to get some good ideas for how to sculpt a world that will interact nicely with your heroes. If you’re an experienced FATE GM, check this out anyway. Your players may be worried that the aspects they chose won’t be especially useful in your setting, and this article may help you convince them otherwise.
Finally, a personal note. I urge all you GMs, DMs, Storytellers, Bartenders and Referees to keep your world flexible. Your current crop of players is the most important group in the world, and if their fun requires that you modify your plans a bit, so be it.