Catch43,
A few more details on how to change it:
In the green buttons at the top of this thread, click Go > My Space > Profile.
On the next screen, click on "View/Edit Complete Profile".
Scroll down to " Avatar / Picture URL: " and click on "Edit".
Then choose an image (there are several pages available) and follow the on-screen directions to select it.
By the way, sometimes it takes a few minutes or even longer for the avatar to show up in your posts. But if it doesn't show up after a little while, try making the change again. Once in a while it takes multiple tries.
Good luck!
Julie