Zoemacara,
I had to learn this just a few weeks ago since I'm not as computer savvy as some of the rest of us. On the item that you want to copy, go to the top of the page and highlight the URL address(left click). Then right click and hit copy. Now go to the page where you want to leave a comment, left click on your comment box, then right click paste. When you submit your comment, the picture will be there. Try it out and let me know how it works!