To point another domain to your main hosting account domain is usually referred to as a Parked Domain. However in cPanel it is called an Alias.
To Park a domain on another domain in cPanel is very easy. First setup is to set the nameservers of the new domain to be the same as your hosting account nameservers.
For help on finding out what your nameservers are check our FAQ: What are my hosting nameservers
For help on how to update nameservers see our FAQ: How to update domain nameservers
Once the domain nameservers have been updated you can proceed to Parking the domain on your cPanel account.
Login to cPanel then click Aliases ➜ type your domain name into the form ➜ then click Add Domain.
Once that is done your domain will start pointing to your main domain website. You can also add new email accounts or email forwarders for the new domain in cPanel.