You need to upload an image to photobucket, flickr or similar and copy the URL (link code) back to the image.
If you want to check you got the right URL open a new browser window and paste in the URL and hit return. You should see the image and nothing else, no page or text load in the browser window.
Then you go to the "My Home" link here in the forums, click on the "edit" link next to "Personal information, email, password, etc. "
Scroll down to the "URL to your avatar (150x150 max pixels, may be smaller) (.gif, .jpg, .png accepted)" radio button, select it and paste the URL to your image in the text field below it, then hit the "submit" button.
That should about do it.
