Originally Posted by Redneck

Cancel that.

You earn "milbucks" by making posts, answering trivia correctly, or being the monthly winner in the arcade. Once you have earned enough of these milbucks, you can go to the forumPX (link is in the upper left of the main screen) and then to the "forum special effects" section, and purchase the avatar privelege, after which you simply go to your profile and at the very bottom there will be a section for the avatar. Choose either one of the on-site avatars or upload your own, and you're good to go.