It's not as complicated as it sounds. As long as your picure is fairly square, one of these things should work:
If the picure is on the internet just drag it to your address bar and you should end up with it on a page by it's self. Then just copy and paste it onto my settings<my forum settings.
Or drag the picure to your desktop then go to imageshack.us to host it. Copy and paste the link marked, "Here is your direct link" onto my settings<my forum settings in the designated place.