Adding images to your post is as easy as right clicking on any image on the web to find out what it's URL (web address) is. Once you know it, just place it in your message, then when you hit 'post' it magically appears.

So for the image I just posted here I typed in (actually just copied & pasted): http://www <www>. followed by photographica.org/photos/archives/010702-0920cs-arrest.JPG