You can just add your adsense code to the new sites. You don't need to do anything special within adsense first. Now, if you want to be able to track clicks and impressions between the two sites, you should create a new channel in adsense, but that's just for better statistics on your side. If you just want to get the adsense on the new site, just add it.
you just have to add the adsense code and if you want to keep track of those you just make a channel and wala you have everything done. its simple once you know.
You can have Google Analitics to track more info about your site also...but you must to ask them and they choose if you receive it or not