You can easily create addon domain in cpanel and for that you just have to follow below steps:
- Login to cpanel.
- Click on "Addon domains" in "Domains" section.
- With this option you can add additional domains in cpanel, but you need your hosting provider's permission.
- Enter your domain name, subdomain and document root path.
- Click on "Add domain" and you will get message that "Your addon domain has been created".