1- Sign in to your Google Adsense account.
2- Click on My Ads tab.
3- Then from left side click on Domains and then Hosted Domains
4- Click on new Hosted Domain.
5- After that Add domains(s) in the box or upload a CSV file containing domain names and Click Submit
8- After completing DNS process just click on Request Verification.
10- Here is the Preview.
If your website is not Active and ads are not showing i suggest you to please wait at least 24 hours and double check your settings.Otherwise post here the problem you are facing.