Well for the most part what I would do is stalk your chosen forum's OOC (That means out of characters) and see which one is not too full. Or you could just find an Interest check and apply your interest there, stick around until the original poster decides to make an OOC for it. There are also three levels of writing here.

Free is low standard. One liners, bad grammar, bad spelling, shallow characters, you could make those there. That being said, the creative freedom in the Free section can churn out some interesting stuff.

Casual is your around alright place. Higher standards than free but doesn't hold itself as seriously as Advance. Not great, not horrible, generally pretty good, but can also be pretty bad.

Advance is high quality stuff. You don't often find a badly written Rp there, but they demand a lot fron you. they tend to also go rather slowly due to their length, but woe to you if you find a fast pace advance level RP who's players churn out walls of text by the hour. It does happen.

We also have Arena, a place solely meant for players to create characters to fight others. never been there myself.

There's also the Nation section. Like arena, I've never been there, but I imagine that there you can create your own nation and deal with other nations in the same forum. I dunno, never been there.

If your interested, me and a friend are making this sort of Virtual Reality Game/Slice of life that could use a small group. If your interested of course.