It’s easiest just to use Graphene’s built-in Adsense options:
Graphene Options >> General Options >> Adsense Options
and enter the code you have there. (You don’t need to sign up with Adsense to use this; it will accept any code from any ad service.)
You can also enter that code in a text widget and put it wherever you want. See these tutorials on how to manage that:
http://blog.kjodle.net/2011/09/12/fun-with-text-widgets-part-one/
http://blog.kjodle.net/2011/12/05/fun-with-text-widgets-part-two/