To add new a Domain name, follow the below steps.
Login to your cPanel.
Click on Addon Domains under Domains tab.
A form to add new domains will appear. There type in the new domain name you want to add along with the directory name and password.
To remove an addon domain, follow the below steps.
Go to Addon Domains under Domains tab.
From the list of domains, select the domain you want to remove and click Remove.