Where do I put my adsense code in the simplicity theme?

[flavor8]

Hey guys, I have the simplicity theme setup, and love it. However, haven't quite figured out what file does what page yet...

I'd like to place google ads in the blank space on the bottom left on posts -- see hxxp:mainactor.flavor8.com/index.php?topic=3.msg3#msg3 [nonactive] -- what file is that in?

Thanks in advance