I think you meant how to setup your signature in general. If it is the case, you can go to "User CP" (user control panel) >>edit signature. There you enter whatever you want for your signature including a link to your website.
On the Top of the Forum page you have a Edit User CP, there itself you can change the signature, but do this not for promoting your site.. as now a days there are many rules which forum moderators have implemented..
I believe at DP, you can NOT have your signature setup until you have 10 posts. That is the rule. You can doublecheck it just to make sure.
Some people expect to first receive, than give later... First contribute, and find out later how to get back linked from this site Just my 2 cent, Epage
I know how to put my signature on digital point thanks for all the reply's But what i was after was how do i put my sig no a page that just has a plain comment box.