Here's how to upload a profile picture (avatar):
1. Click on your screenname, on the gray navigation bar at the top of your page.
2. Click on "Change Avatar" under your profile picture. (You may have to re-log in)
3. Scroll down to your Avatar picture and click edit.
4. On the next page, click the "Browse..." button and select photo you want to upload. The photo should be saved somewhere on your computer.
5. Once you've selected the photo you want, click the "Preview Photo" button. The new and old photos will appear at the bottom of the page.
6. If you're happy with your photo, click on the "Save Changes" button.
Note: Profile pictures are also called avatars.