its easy to take pictures. Just press F1 first (to hide the GUI) and then F2. Once you do that, go to the minecraft directory (.minecraft). in the folder screenshots should be your picture. Take that out and upload the picture to an internet website. Any, as long as you have a specific address for the picture. Once that is done, use the insert image tool in the reply editor (written like this:[ img]http://[image URL goes here][/img) and you have your image!
And pics or it didn't happen.