In cPanel, click on “Domains”, located in “Domains” section.

Click the "Create A New Domain" button on the right side, fill in the "Create New Domain" form with the top-level domain or sub-domain you need to add. And then click "Submit" button to add the new domain name.

If the domain is not a separate website and points to the primary domain, please tick the "Share document root".

Generally, you can use the default value for other options. Or change the settings according to your demands.