Well, first of you need to print the image that you want out.
Then you take some glue and stick it to your screen the moment you're gonna post a... Post.
Your screen will scan the picture and ta-da. Picture is added to your post.
>click the image icon if necessary to see the url tab
>copy/paste the url into the bar
>add ".jpg" ".gif" or ".png" to the end of it, depending on what it is.