Each cPanel account has a 'main' domain associated with it. This is the domain that points to the public_html of your web space and used as the main reference label for everything under the account. Unfortunately, it's not possible to change the main domain from within cPanel itself - this can only be done through a support ticket.
If you would like to change the main domain on your cPanel account, please bear in mind that the domain you want to change to can't already exist under the hosting package. So remove the domain you want to make the 'main' domain if it is already added, and then when you're ready to request the change please raise a support ticket and we can make it the main domain on your account.
We would generally not recommend changing the main domain of a live site because of the upheaval that it can cause. What we would recommend is using the cPanel Domain Aliases feature to point a domain to the public_html, and then using a canonical re-direct either in your .htaccess file or the application itself. In the case of WordPress, this is a case of going in to the wp-admin area, and then setting the Site URL and Homepage to the new domain.
Updated almost 2 years ago