Step 1: Login 

Login to your cPanel account and click on the Addon Domains icon under the Domains tab.

Step 2: Add Domain

In the New Domain Name field, enter the name of the domain you would like to add to your cPanel account.

Step 3: Name Directory

Enter the name of the directory which will contain the files for your Addon Domain's public website. 

Note: By default this directory will have the same name as the domain you have selected and can be left like this

Step 4:  Create Password

In the Password field enter a password for your new Addon Domain. To finish click Add Domain, your domain will now be added to your cPanel account.

Note: This password can be used to access the domain via FTP.