First click on the profile button
in the menus at the tops and bottoms of all the forum's pages. Once your profile comes up, click on "Forum Profile Information" under the heading, "Modify Profile". Then you can choose a new avatar photo from the ones provided in the window to the right of "Personalized Picture:" (clicking on the name of an avatar will display it to the left of the window so that you can see what it looks like), or, if you have your own photo stored in your own Web space, you can enter the URL for the photo in the box to the right of "I have my own pic:". To change the text that will appear below your new avatar, simply type something new in the box to the right of "Personal Text:". And once you've gotten everything the way you want it, scroll down the page and be sure to click on the "Change profile" button to save everything.
Good luck.