What are you trying to change in your profile? Also, this is probably a dumb question, but are you clicking save on the bottom after you make the changes? lol
To change your avatar: When you're on the forum, click "Profile" near the top underneath the main banner (next to "Usergroups" and "You Have __ Messages"), and then click "Avatar", which is a little below that and next to "Signature" and "Friends and Foes".
If you still can't find it, let me know.