An avatar is the photo or graphic that appears with each of your forum posts.
Unfortunately, I don't have the ability to add an avatar to other users' accounts--only my own! But since it's not immediately intuitive, here is how to add your own avatar photo from your computer:
First, login to the Forum (you've probably already done this by now).
Then, select the grey "Profile" tab.
On the blue bar ("Profile for..."), at the far right, click "EDIT".
This opens the profile page: click the "Avatar Image" tab.
Look for "Upload New Avatar". You can click the "Choose File" button and search for it on your computer.
If you upload your own picture, you can upload an image up to 250 x 250 pixels and 50 kilobytes. The forum will automatically scale the image for use in various locations.
Once you've selected the file, you'll have to scroll ALL THE WAY TO THE BOTTOM of the page, and find the SAVE button. Click this, wait a few seconds, and you're done.
Have fun! We hope to see a lot of new avatars out there!