It's really easy. Honest.
At the top of this web page click
Quick Links> Edit Signature What ever is in your signature will appear at the bottom of all your posts. In the text box enter
[url =
address of your gallery]My gallery[/url]
Obviously you need to replace "address of your gallery" with the actual URL to your gallery. Also make sure that you don't have any spaces between around the equals sign. You can also do this by clicking on the World with chain icon and another window will pop up and walk you through entering the info.
HTH! Holler if you need more help.