"Sing up"? Not sure what you mean. If you mean "Sign up", as in "register" or something... There is no such thing. You registered for THW, you're now set to talk or do things in (just about) every forum (except Medivh's Tower, which requires approval, and anything else not open to regular Users normally (admin threads, etc)).
Also, I'm just a random user, like yourself. Notice how my name doesn't have any titles or whatever by it? These questions are great for someone like a Moderator or Administrator. Also, we even have a special sub-forum/thread for "Site Help" or something like that. Just poke around; things'll start to make sense.