1) Accumulate 25 posts or more
2) Click on the top of the screen on the left side where it says "User CP" (along with other options such as FAQ, Member List, Calendar, etc.)
3) Options will be listed along the left side of the screen
4) Click on Edit Avatar (5th option down)
5) You MAY have to click on the "Use Custom Avatar" choice. It will probably be set to "Do not use an avatar"
6) Either enter a web address for a picture or choose to upload one from your computer. IT WILL HAVE TO BE 100 X 100 PIXELS OR LESS.
7) Click the "Save Changes" button
8) Done.
Hope this helps.
H-D