How to add an avatar-

Click on your "User CP" in the top left corner.
Click "Edit Avatar" on the left side.
After you've saved the picture you want to use to your computer, click "browse" and select it.
Save changes.
(If you have trouble adding the picture, it may need to be resized).

How to Edit Your Signature-

Click on your "User CP" in the top left corner.
Click "Edit Signature" on the left side.
In the message box you can add whatever text you would like. Highlite the text to change the font, color and/or size.
If you want to add a picture or ticker first upload them to a site like www.photobucket.com (an account is required. It is free)
Copy and paste the HTML or IMG code into the space at the bottom.
Save changes.

Options-

From the options menu, under your User CP you can change many things.
Use invisible mode, email notification of threads you are subscribed to, private messaging settings, show signature, avatar and image settings. You can also change the "view" that you view threads in, posts per page and time zone.

Profile Picture-

A profile picture is a picture that a member sees when they view you profile. To add a profile picture, follow the same steps as adding an avatar. (If you have trouble adding the picture, it may need to be resized).

From your User CP you can view all of your private messages, start a private message, show your subscribed threads, buddy lists and ignore lists.