Question: How to add Park Domain for any website in HC panel?

Solution:
To access a domain with another name, you can add Parked domain for that website. Both Parked domains and host headers serve the same purpose. While adding a host header from HC panel, a host header value is added against a website WHEREAS adding a Parked domain automatically adds a host header and also puts an entry of Parked Domain in HC panel against that particular domain.

Now to explain how Parked domains work, Let's say you have a domain named mysite.com and you want to access the same domain with mysite1.com and mysite2.com. Then you will simply follow these steps:

You will navigate to the menu Domains :: My Websites :: Website Properties :: Parked Domains in HC panel and would add the Parked Domains mysite1.com and mysite2.com respectively. Now when you will access mysite1.com OR mysite2.com it will show you the same pages of the actual website mysite.com.

Note: The Parked Domains should also be registered domains.