Hi everyone!
Welcome!
What WhiteComic said! There's lots to see and do here, but take time to get to know the place. Especially check out the FAQs and Policies (more especially those relating to Adult and Mature Content, and why duplicate accounts are verboten).
If you intend to run a game (be a Game Master, Dungeon Master, Referee, etc.), then you will have a steeper learning curve, but that's because this site offers one of the most powerful toolkits for game creators anywhere. I mean, seriously, it's like they designed it that way or something, y'know? ;-)
If you want to start out playing, (probably what you'd want to do if all this is new to you) then look around in Wanted - Players for a game that might interest you.
Game Proposals, Input, and Advice might also be a good place to look for games that are in their infancy (the planning stages). Sometimes it's a while before a new game is actually ready, and it's a bit of work getting a new game off the ground (so to speak), so patience is the order of the day here.
Don't be afraid to ask questions. Community Chat is a great place for that, or for just hangin' out. There are other places for more specific game-system and technical questions, and these have specific rules in play that are given in their Notice topics (stickied to the top of their topics lists).
As you get more in tune with how things go, you'll eventually find the games that make your day. Dig in! Adventure awaits!