froggy, I'm not sure guy, i think that they need to be hosted online somewhere
for example, if I saw a pic on espn.com, do a right click on it and see the "properties" of the pic, then copy and paste the url. you need to click on the icon that looks like a picture in your "post a reply" window, click on that icon (just to the right of the "envelope" icon) and paste in the url
Again, I don't know how to do it if it is just a pic on your hard drive