Your "Primary Domain" will already be setup in cPanel, but you can add additional domains in cPanel by creating them as "addon domains".
To create an addon domain, do the following:
- Login to cPanel in a web browser
- In the search bar at the top, type "addon", then click on "Addon Domains".
- Here you can view / modify existing Addon domains, or create a new Addon domain
- To create a new Addon domain, type the domain in the "New Domain Name" text field
- click on the "Subdomain" field to automatically fill in the text for the subdomain and document root, based on the domain name you already typed in.
- Click "Add Domain"