Ok...
If you want an avatar from the list, click the radio button that says 'no' (it's near the top of the page), then just click the radio button of the picture you want and then click 'change avatar'.
If you want to use a pic elsewhere on the web, click the radio button that says 'yes' (it's under the list of avatars), then type or paste its url in the box that has 'http://www.' written in it, then click 'change avatar'.
If you want to use a pic on your hard drive, click 'browse' and find where it is located on your computer. Once you've found it and clicked OK, it'll start uploading. When it's finished, THEN click the 'yes' radio button (you can do it before, but it'll just jump back to 'no' after uploading), then click 'change avatar'.
Hope it works out for you... and angry slig is bad enough, we don't want a furious slig.