New world forums are created after the designer has shown a great deal of commitment to their world. So you are looking at 50 or so quality informational posts before we will even consider it. (Look at the Arth Thread in the Arth forum to get an idea).
Put your world in one thread. If you break your world into several thread, then tend to get lost and nobody replies to them.
If you are creating a world for a free-form game, do not forget to link the setting thread with the game thread.
Creating a freeform game is fairly simple. Just go to the right forum and make one. If you make a game in the wrong forum, we will probably just delete it.
There are FAQs around here that you should follow. Bother to read them, or game at your own peril.