first you have to upload them to some place like photobucket or something. Then there's actually a code that you can just cut and paste right under your uploaded picture. Or, upload your pic somewhere else and put it in img codes.
picture address.jpg[/IMG*]
(take the * out after the /IMG)
you can upload them directly from your computer. Hit Post reply... above the "quick reply" then go to the "manage attachments". make sure they're of appropriate size or it won't do it. or, if you host the pics in something like Photobucket, use the IMG tags.