Redirecting the naked domain http://mail.mycompany.com to http://www.mail.mycompany.com

Redirecting the naked domain http://mail.mycompany.com to http://www.mail.mycompany.com

Hello,

Currently i am using custom URL , for example: http://mail.mycompany.com to access my emails from zoho.
What settings do i need to perform in order to access my zoho email with URL www.mail.mycompany.com
The domain is registered with godaddy.com

Looking forward for your help

Regards,
Admin