Click on SETTINGS at the top of the page. Click on Avatar Settings (or profile pic seems to work too). Get yourself an avatar pic in there, then click on one of these quit banners you see that most of us have and when you get a few posts under your belt you can have your signature posted whenever you make a post. When you click on a quit banner it will take you to a page where you can input the relevant information and then it will give you an embed code. Put that embed code in your signature section of your settings. Done.
If you don't have an avatar you can always make a free Mangatar at
create your mangatar | mangatar. This way you don't have to show your real face which is nice like when you want to be a ninja or if you are really ugly and you want people to think you're awesome

Just kidding. It's a cool site, use it if you want.