How do I add a new email address?

This is a plumb newbie question, but I would like to add another email address to my domain.

Example: myprimaryemail@widgets.com, and I’d like to make billing@widgets.com

Same user, just different addresses.

Thank you.

You can do that with an alias if you like,
You need to go to Mail -> Aliases and add billing@widgets.com as an alias to myprimarymemail@widgets.com