K let's see if I can help you...i know how to do it but telling someone else is hard for me!
First go to edit your siggy then click on the globe with the link in front of it. where it says URL, type whatever address the dogster page is. Then once this is in your siggy, highlight it and type Dogster or whatever you want. If that didn't make sense, ask questions and i'll try to help! sorry i'm not a good "explainer"! lol