in the 'quick reply' below the thread or when you click 'post reply' there is a yellow icon of a sky with a mountain and the sun. if you have already uploaded the photo somewhere like imageshack you can put the link for the photo there.
in 'post reply' under the text box you write in there's a hyperlink that says 'Click here to Upload a Photo...' Choose a file to select your photo then Upload Now.
