This article outlines how to create an Alias Domain in cPanel
Adding a Domain Alias
To add a domain alias, enter the domain name in the text box and click Add Domain.
To open the alias domain's home directory with cPanel's File Manager interface, click the link that corresponds to that alias under the Domain Root column of the Remove Aliases table.
When you create an Addon Domain, Parked Domain, Subdomain, or main domain, the system will attempt to automatically secure that domain with the best-available existing certificate. If no certificate exists, the system will generate a self-signed certificate to secure the new domain.
If AutoSSL is enabled for the account that owns the new domain, the system will add a request for Domain Validation SSL (issued by trusted Certificate Authority) to secure the new domain.
Further reading: Creating a Subdomain in cPanel.