Halo and welcome. You may not have the ability to do that yet,althought you can log on and semi-edit you page. The mods will send an activation to your e-mail once they have activated your status. Some one above posted how you can actually edit your sig and avatars. So if you can't do what they advised then the above may be your cause.
PS: It to me almost 3 weeks to get activated on here,but in the mods defense thet are busy people.xd