1) Login to your AdSense account to generate AdSense code.
2) Login to your GPC account and look for 'edit HTML'. If you cannot see it, press F11.
3) Insert your AdSense code anywhere you like.
4) Save changes to publish the page and your are done.
Don't view your GPC website too many times for testing because this will increase your page impressions and your AdSense account may be banned by Google. The source of this information is from
A Short Introduction to Google Page Creator (GPC)
Google Page Creator has launched for about a year. It is another project of Google lab. GPC enable users to build a free website without having to learn HTML code. Google will host all the GPC sites and the domain name for a GPC site will be http://yoursitename.googlepages.com. You need a Gmail a/c when signing in to GPC to create your webpages. If you want to test drive GPC but don't have a Gmail a/c yet. Here's the link to sign up
Another way to get a Gmail a/c is ask your friends or family members to request Google to send an invitation email to you.