First, you'll need to log in to your CPanel Account. If you didn't already do that, use those instructions to login to your CPanel account.
Once inside CPanel, locate the EMAIL section and click on Forwarders
From there click on "Add Forwarder"
Fill in the details in the next screen
The "Address to forward" is the alias / mail group / forwarder you're trying to create (e.g: firstname.lastname@example.org)
Repeat this step for all people who should get the copy (e.g: email@example.com could be sent to you, your assistant, etc...)