If you've signed up for Google AdSense on one of your sites and are ready to expand onto a second site, do you need to ask Google for permission, or can you just start displaying AdSense code on the second site? The answer is that you can just expand your AdSense horizons without checking in, as long as you ensure that each and every site you use meet all the criteria of the AdSense program. it's important to make sure you don't err, however, because if you add AdSense to an inappropriate site, you risk being kicked out of the entire program, which most assuredly wouldn't be a good result. So, take the time and please read up on:
Adding Sites to your Google AdSense Account
And if you haven't yet signed up for Google AdSense, please pop over and read my popular tutorial Getting Started with Google AdSense.