Press the key that says:
Print Scr
Sys Rq
And then open up MS Paint. Click on the tool with a perforated rectangle for the icon in your left tool bar, and then right click the white space. Select paste. Save the picture, and then open a web browser. Go to imageshack.us. Click Browse, find and select your picture. Then, click host it!. When it is finished, copy the direct link on the page. (It is literally labeled, "direct link".) Then, paste it into a post, then highlight it. Click the picture of a photo up in the icon bar used for posts. Then, post.