Click your username in bold at the top-right of the screen. That should take you to your profile.
Click "Customize Profile".
On the left side you should see a nav bar with blue headings. Find "Edit Avatar".
You should be in a screen with a lot of fish pictures and radio buttons. You can use an FL avatar or scroll to the very bottom of the screen and either use a photo from the web, or upload your avatar from your computer. If the file is too large, you may have to scale it down some, but the site will autosize most images for you.
