You need to have the photo hosted somewhere first, I like photobucket.com or you can also use the tpunk gallery. You copy & paste the URL into the body of your post, and make sure you put the [img ] tag before and the [/img ] tag after the link. Please note that I had to add spaces to the tags or they don't show up in the post. You wouldn't have spaces between the letters and the .
[img ] http:// www.photobucket.com/
indierock'spicturelinkhere/html [/img ] Obviously I just made that link up. But that's how it works.