You just need to copy the tags from all the pictures you want! Have you managed to find the Image tags?
Using Snoops example, you can see how multiple images can be listed in one post.
Hope that makes sense?!
In Photobuckrt you select/tick the photos you wish to include
There is then an option to generate the BBS code for the ones you have selected. This is copied automatically to your clipboard for pasting in to your forum reply.