Follow these steps to park a domain in cPanel:

1. Log in to your cPanel account.
For instructions on how to log in to your cPanel account, please click here.

2. Under the Domains section, click Domains.

3. Click the Create A New Domain button.

4. Enter the domain name you wish to park onto the account, leave the 'Share document root' option ticked, and then click the Submit button. (If you have 'Share document root' enabled, the domain will show the same content as the main domain on the account. In this example, "create.example3.com" would be an alias for "demo.com".)

Note: In recent updates, cPanel has migrated the functionality of Addon Domains and the creation of Subdomains under the Domains section, combining them.

5. Once completed, it will take you back to the Domains page, where you can see your newly parked domain. Notice that "demo.com" and "example3.com" share the same document root.