By clicking on Profile you can edit your forum profile. Here's a small guide for n00bs.

Information
Username: Obviously, here you change your username, which is the name members of these forum will recognize you by.
Password: Obvious.
Personalize Information: change your gender, birthday, location, interests, etc. (this is seen by other members)
Contact: add your Skype, website, Yahoo, etc.

Preferences
Change your preferences on what notifiations you recieve and how you view the site.

Signature
The signature is the picture, words, etc. that appears under each of your posts.

Avatar
Yor avatar is your profile picture people will recognize you by.

Friends and Foes
Friends:Peope you often contact.
Foes:Blocked users.