dude there is no need for paid subscription. Go to your profile settings and add your signature

Ha! I never even thought about it. I am glad you asked the question. Guess i should go fix up mine now. Isn't there a guide available about this type of stuff?

That's nothing. Go click your username at the top right corner. In the page that appears search for and click on the link "customize profile" near the "Mini Statistics" box and in the page that appears click on "change your signature" in the left of your screen. simple

The "user CP" button on the left side of the red bar at the top of the page will give you all sorts of options of things to do. Sig file is one of them.