First go to the site of the ticker that you like (you can find that next to the ticker). Follow the instructions on how to make the ticker, then copy and paste into your signature (following the ticker sites directions) by going to "User CP" at the upper left corner of this page.
This is a very general direction of how to do it. Once you find the ticker site you like and you still have questions, let us now and we can go step by step.