A Addon Domain is an additional domain inside of cPanel. This means that a Addon Domain has its own location (document root) for all of the html files. It is separate from the primary domain on the account.
To use a Addon Domain you need to login to your cPanel account.
Find the “Domains” section in cPanel and click on Addon Domains (See pic below, click on picture for larger version).
You are now presented with the following screen for adding a new Addon Domain (See pic below, click on picture for larger version).
You will need to fill in the following fields. If you use tab after entering the New Domain Name, most of the fields will be filled in for you
New Domain Name: This is the domain name you would like to add. This is just the domain, do NOT include ‘www’.
Subdomain/FTP Username: This is the unique username that can be used for FTP access to the domains Document Root. This is important primarily for people providing developers access to their site.
Document Root:This is the path on disk to where the files for your new addon domain will be stored. It is based off the public_html file structure. This folder will need to be created after setting up the addon domain.
Password: This is a unique password for the FTP user created above. This should NOT be the same as your cPanel password for obvious security reasons.
Strength (why?): This is the strength meter of your password you created. This should be green. You can use the password generator to create a unique password for you. Please be sure to remember this password as it is not recoverable, but you can change it again.
You can now click on the Add Domain button, if all the fields are filled in.
A list of Addon Domains, if any exist, is listed below. You can see the domain, document root, username, and if it redirects. Under the Actions area, you can manage the redirection and remove the Addon Domain completely. This does NOT remove the document root folder or the contents.