In order to have a new domain pointed to a subdomain on your site you will need our extra feature called "Addon domain".

In order to use an addon domain you should have an addon slot and an additional domain name. You can purchase them from your Customer's area, the Order tab.

After you purchase the addon slot and the domain name, you have to add the domain to the slot from your cPanel > Addon Domains. For more information on how to do this you can check our tutorial.