In order to create a new email address in your Cpanel hosting plan you will first need to log into the server.

https://yourdomain.com:2082 <- yourdomain.com is replaced with your domain name

Once logged into your control panel under the Mail options click "Email Accounts", It has a picture of an envelope.

From there you will need to enter the email address and password, as well as assign the mailbox a quota (optional). Then you must click "Create"