To set up a custom domain, You must log in to your Cpanel.
Now, navigate to Domains under the DOMAINS option. Click on the Domain to click to view the interface.
This is how the Domain section looks
Now, click on Create A New Domain
Now, you will be redirected to a page where you will be able to set up a new domain. 
Enter your domain name in the Domain text box
Finally, click on the Submit button. 
You can also create a different document folder other than your root folder. To create a different folder, just uncheck the small tick mark you see here. 
After unchecking the tickmark, you will see another field where you can specify the directory name.
