How to Host Additional Sites Using Addon Domains in cPanel
What is an "Addon Domain" and how do they work?
An addon domain is a domain name that that points to a subdirectory within your account. For example, you may set up “mynewdomain.com” to point to “myfirstdomain.com/mynewdomain.com/”.
The add-on domain will look completely independent to the outside world with no means for anyone to know that this is running on your main account under another site. In order to use an add-on domain you first need to purchase/register the domain and then configure the add-on domain using cPanel as documented below.
Configuring Addon Domains in cPanel
Login to your cPanel and click on Addon Domains which will be in the Domains area of your control panel.
On the next screen you will need enter the New Domain Name that you have already registered. cPanel will automatically fill-in the Subdomain/FTP Username & Document Root fields for you based on the New Domain you entered. Enter a new password for this domain and click Add Domain