Once you have logged into AMP, to change your domain's WHOIS information:

1. Under "Domain Management" click on Manage Domain
2. Next, select the domain that you want to change the WHOIS information for. 
3. Then click on "Review or change your registration details?". This will allow you to change the email address, address, and phone number of the domain.
4. On the next screen you can make your changes.  Click Edit by the details you want to change and fill in the new information.
5. Once the new information is added, click on Submit.