In order to attach pictures, they must first exist either in your computer or somewhere on the inter-net. If the pictures are on your computer, look below the "Reply" box (where you type messages) when at the "Post reply" window.
You'll see a function called "Attach file." There is a "Browse" button there, which you enable; and that brings up a "Choose file" window, where you navigate to the picture you wish to attach.
When you've found the picture, highlight it and then enable the "Open" button on the "Choose file" window. The picture will then appear at the bottom of your post once you've enabled the "Submit reply" button.
Bear in mind the fact your picture cannot be larger than 33.2 kilobytes and must conform to the "Valid file extensions" listed beneath the "Browse" button. Also, at this web site, you can only attach a particular picture once!
Now, if your picture exists elsewhere on the inter-net simply save it to your computer and follow the steps above. If your picture is an actual photographic print, you'll have to scan it and store the scan in your computer (then follow the steps above).