First of all, host your pictures at a site like
www.photobucket.com or another picture hosting site. Then you would have to post the image using a code, which photobucket is one that provides a code, like this:
[IMG]
http://url.jpg(file location)[/IMG]
I put a dummy url, for example, it would need to have the [IMG] tag in front of the url and [/IMG] behind it, to host the pic, but all one line, not interrupted like mine to show the example, as the one below:
