How to make it so my forum is centered
 

I was wondering how do I make it so my forum is centered? equal size on each side? an example would be :

www.berry365.com

My site is www.BlackberryOS.com

I still want the side column on the right side with the banners but as well as space on the other side if I want to add smoething else. would I just have to create a left side bar column as well to obtain that look?