Hi V8am, Nice to meet you.
You need to visit Gravatar.com and sign up with your AB email address (i.e the one you can see when you go to "my profile" and click through "edit user details") and choose an image.
under the "edit user details" page there is a tick box at the top of the page. If you want and Avatar, click it, and scroll down to the Submit button at the bottom of the form. Once submitted you should be able see you avatar on the main site next to your posts.
All the best,
Spare Ed