I won't delete Mash Potato because that would delete all your posts, too!
To include an image you need to upload it to a server somewhere, perhaps an MSN account or you're probably got room with your email account to put stuff on the web. (I'm sure someone can suggest a good free place to upload pics.)
Once this is done, just put the url (ie the www link), highlight the link and press the Img button, above.