Visit Imageshack.us
Browse for the file you would like to use
Once it has uploaded in imageshack, copy and paste the link that says 'direct link to image'
Come onto edforums, and start a new post (or reply to one)
At the top, click Image.
Straight after this, with no spaces, paste the link to the picture
Click Image again to close, again, no spaces
The image will appear!