How to use signature for free for my self?
Go to "PROFILE" first, and there you will find " Forum Profile Information". There you can set up your " Personal Text" or " Signature" and other things.
Deference between ranks is in how many characters you can put in signature, and colors in signature. Also when you become full member you will be able to put some avatar.
I hope I helped you with this, you could find all this informations just you needed to look around a bit, and learn to use search.