Evan,
If you have it downloaded, and you have a image open, click "ctrl" and the "R" on you keyboard.
When the sizing window opens up, click on the right side, "800x600"
This size is usually pretty good for GCA's discussion group. Now click "ctrl" and the "S" keys and save the image accordingly. You should be able to post it from Photobucket fom there with no problem.
If you have problems, just IM me and I'll walk you through it further.