Adding a new domain name for a current website to respond to is super simple.
Before you proceed, please check with your technical team to make sure that the domain name is correct and is currently pointing to the correct place (DNS and web server). Not doing this may result in an unresponsive website. Also, you might need to ensure that your licensing will not be impacted.
Adding a New Domain Name
First, make sure you're logged in as a superuser. You can tell that, because you'll have a "Host" menu appear in your control panel.
Now, in either the "Content" or "Admin" menu, find and select the Site Settings view.
This will open the Site Settings page. Find the section on the Advanced Settings tab called "Site Aliases." This is where your domain names are managed.
Next, click on the Add New Alias button. This will allow you to enter the new domain name that your website should be responding to.
Enter the domain name and double-check the spelling of it. Until you're 100% certain that the domain name is working, don't check the checkbox to make it the primary yet. You can come back and do that later. Click the save icon to save your changes.
Now, scroll to the bottom of the page and save your changes.
All that's left to do now is to make sure that the domain name is working. Attempt to visit your website using the new domain. If it doesn't work right away, don't panic. In many environments, it may take as much as 24 hours for domain name updates to fully work.