To add an addon domain, we can use cPanel’s Addon Domains feature, in the Domains section of the cPanel interface.

1. Enter the domain name in the New Domain Name field. In this case, we will enter cpdocs.com.
2. Ensure the FTP username is appropriate in the next field. In this scenario, we will leave it as its default value, cpdocs.
3. Make sure that the document root is in the appropriate place. In this example, we will use the default value, /home/$user/cpdocs.com/.
4. Enter and confirm the password you want to use with this domain in the appropriate fields. Note- There is a checkbox to create an FTP account when adding your addon domain. Unless you specifically need an FTP account for the addon domain (i.e., allowing limited access to a developer or similar), we do not recommend creating this FTP account.
5. Click the Add button.

If you see an error in this interface, that means that your hosting provider has not enabled this feature for your account, or there may be another problem. Please contact your hosting provider to fix the error before continuing.