Step 1. Login to your cPanel account and then select "Addon Domains" under "Domains" section.
Step 2. Next is you have to fill out the all information under "Create an Addon Domain":
New Domain Name: Enter your domain name.
Subdomain: Subdomain will be filled automatically, If you want to create your own subdomain then enter your subdomain name.
Document Root: Document Root also will be filled automatically, but if you want to create different directory name for your domain then fill the document root.
Create an FTP account associated with this Addon Domain: If you wish to create an FTP account for your domain name then tick the Create an FTP account associated with this Addon Domain option. Below are the information related to FTP account:
FTP Username: Username will be filled automatically, If you wish to use your own username then fill the username field.
Password: Enter password for your FTP account or Generate a password using the "Password Generator" button.
Password (Again): Repeat the same password that you have filled in password field.
Step 3. Once you have finished filling then select "Add Domain" button.