If you want to change the domain name that identifies your hosting plan, that is, the main domain, you can do so in a few clicks!
Step 1 - Check the Domain
First, make sure that the domain name you want to set as main is visible in the Websites section of your panel. If it’s not there, make sure to add the website first.
Step 2 - Change the Main Domain
Go to Websites → Manage, search for Set Main Domain on the left sidebar and click on it:
Open the drop-down list and choose the domain you want and click on Set as main domain:
If you don’t need the old website anymore, you can delete it by following these steps: How to delete a website.
NOTES
The Set Main Domain feature only renames your hosting plan. It has no influence on website files
The option to change the main domain is not available for websites created with Website Builder