Sure thing, viewtiful. To get an avatar, you'll need to find a picture you want to use and resize it so that it's 64x64 pixels or under. Then, you need to upload it to an image host (I recommend
Photobucket). You'll then have to go into your profile, find the place where you can enter the URL and put your image's URL in there. To get the URL (if you don't know), either right-click on the full-sized image (if it's in a thumbnail gallery, you should have to click on it to get there) and select "Properties". Highlight the URL and then right click and select "Copy". Then, go to your Profile on the PGC forums and paste the URL into the box. If you're using Photobucket, it lists the URL underneath the pictures in the main gallery, so you shouldn't have to do any right clicking or anything.
That should get you up and running.