if you want to attach stuff is with the paper clip, however to add you may need to use a host like photobucket and then embed here, if got stuff on a blog you can also click the add image button and add the url there.
you either can use image hosting, like photobucket or imageshack and then take the forum html or it is a buttom to add an image, if the image is too big it will shrink to fit the forum layout.
the second option is if you want to add the actual picture and not attach it. what is strange is that the text is a link to your full screen picture. btw, really unique tree shape... keep them coming!