What you need to do is log in to your control panel and scroll down to Email. Underneath that, you will find the Accounts icon. Click on it, and it will take you to where you manage email accounts.
Once you are in the email account management section, you will see "Add Email Account." Here, you enter the email address you want and the password you desire, and then you can choose the email quota. After entering all the information, click on create account, and you will have added an email address.