By doing this you can then have google adsense displaying google advertisements on the index pages of those namecheap parked domain names. You do nothing with regards to the advertising. You just set up Google Adsense For Domains and let google do the rest. Google Adsense For Domains acts the same as Google Adsense For Content in terms of advertisements being displayed and you get paid.

NEVER EVER promote your parked domain name, either before or after the set up of Google Adsense For Domains,