You can upload an avatar from your computer in your Profile section but you have to have an URL for your graphics/pictures in posts and you use the UBB codes to show an image here. If you don't have your own site, there are lots of really inexpensive or free graphics hosting sites like http://www.tinypic.com/ or http://www.photobucket.com but your ISP site should give you a "free" Web site and you know its reliability and can trust it better/ask questions? You can often upload graphics to there and use those URLs.

This post might help you too: http://tinyurl.com/u76oy