You mean when you comment in a group?
If so, join the siggies group and have someone make you one or create your own. Then go to your profile (top of page) to privacy and settings, look for signature and click there. You can add photos or jpg's. I believe you have have up to 6 or 7 siggies and use different ones depending on what group you are commenting in.
at 1:40 PM on Jul. 20, 2010