To create an addon domain, follow these steps:

In the Domains section of the cPanel home screen, click Addon Domains.
Under Create an Addon Domain, type the domain name in the New Domain Name text box.
cPanel automatically fills in the Subdomain/FTP Username text box and the Document Root text box based on the domain name that you specify.
You can change these values if you want.
In the Password text box, type the account password that you want.
In the Password (Again) text box, retype the account password.
You can click Password Generator and cPanel generates a random, strong password for you.
Click Add Domain. After the domain is created, you can add content pages for the domain in the document root directory specified in step 2.
Modifying an addon domain

You can change the document root directory for an addon domain. You can also configure an addon domain to redirect to another domain.

To make either of these modifications, follow these steps:

In the Domains section of the cPanel home screen, click Addon Domains.
Under Modify Addon Domain, locate the addon domain that you want to modify:
To change the addon domain's document root directory, click the cPanel edit icon (edit) icon, type the new document root directory, and then click Change.
To set up domain redirection, click Manage Redirection, type the domain to which you want the addon domain to redirect, and then click Save.
Removing an addon domain

To remove an addon domain that you no longer need, follow these steps:

In the Domains section of the cPanel home screen, click Addon Domains.
Under Modify Addon Domain, locate the addon domain that you want to remove, and then click Remove.
If you also want to remove the addon domain's FTP account, select the check box.
Click Remove to confirm the removal.
When you delete an addon domain, its folder and files are not deleted. You must delete the folder and files manually.
Parked domains (aliases)

Parked domains (which are referred to as aliases in newer versions of cPanel) are often used to reserve or “hold” a domain name that does not have an associated web site.
Parked domains can also be used as placeholders for existing web sites.
For example, if you own the example.com domain name, you can park the domain so it redirects to the primary domain of your Hosting account.