Hello,
Yes, you can add it to your ad-free version. But for those of you reading this who do not have the ad-free version - adsense is a no-no because Google does not allow more than 1 account on the same site.
To add it to your top list you just have to edit your header and add the code there, or any of your list breaks where you want to add it.
I hope that answers your question.