A. [1.] You need to make sure that the new domain you are adding to the host is pointing to the nameservers provided in the Web hosting activation email sent to you when the web hosting service was activated. Then you can apply the Nameservers to your new domain Using the Step by Step Guide on our Knowledge Base link: https://my.registeram.com/index.php?/knowledgebase/article/3/how-do-i-change-my-domain-nameservers-/
[2.] Login to your hosting control panel(Cpanel), and click on the icon "Addon domain" and you can create new host for your domain there.
Note: that you can also call our customers support on phone for step by step guide.