I only recently worked it out too!
When you go to each photo in your gallery click on it to look at it, it will have 3 links down the bottom. You just copy everything in the one labelled code for bulletin board that starts with bracket URL ....... until the other bracket.
Eg Code for bulletin boards:[url=http://www.bananas.org/gallery .........]
And when you paste that code including the brackets into your post, it will displace the picture instead of the code (mine won't work as I didn't copy the whole code)
That is what I did for my post below yours