Domain aliases, are extra domains that you can host in your account. Whilst they display the same website that you have as your primary domain, they can provide a separate email account. Many businesses find this useful who intend to have more than one web address for commercial purposes.
The first step is to log into your cPanel account. If you are unsure on how to do this, please view the following help article - 'How to log into cPanel'.
Scroll down to the 'Domains' section and choose 'Alaises'.
Type into the box your domain that you wish to park on top of your primary domain.
Select 'Add Domain' to complete the process.
The domain that you have entered has now been parked and the process is complete.