Click User Control Panel, up top left of the page.
Click Profile Tab.
Click Edit Avatar Link on left.
Size your avatar per the dimensions stated. (the software doesn't resize it for you).
Upload your avatar. Submit. Voila!
If you need help resizing your avatar, contact me by private message and I'll give you my email address, you can email me your image and I'll resize it for you and email it back to you or upload it for you.