In cPanel you can add Email Accounts and email Forwarders. Which one you choose depends on how you want to use the email address.
EMAIL ACCOUNTS:
If you want to send and receive mail from something@yourdomain.com you should set it up as an EMAIL ACCOUNT and you can use it in an email program like Outlook (Tools/Accounts) and/or our webmail.
FORWARDERS:
If you just want all email addressed to something@yourdomain.com to forward to another address like somethingelse@yourdomain.com or youremail@gmail.com, set up a FORWARD (not a 'real' Email Account).