I think that is not very difficult,just put the code google have given to you to where you want to place.
Have you got your adsense account accepted from Google. If so then follow the email information guidelines sent by google to you. That is in brief.. Log in to your adsense account with your user name and log in password. Find the adsense property infomatin code from your account. Something you will get like Ca-pub xxxxxxxxxxxxxxxxx Just copy this code and put it in your directory template. It is easy. Just try it out. Any difficulty please either PM me or ask it here again. All the best. Happy Adsense Earing.