First, open a browser window, and go to "mail.your_domain_name.com" (replace "your_domain_name.com" with your own domain name).

When the login screen appears, enter the following:

Full email address: your_name@your_domain_name.com
(replace "your_name@your_domain_name.com" with your own e-mail address).

Password: Enter your e-mail password. If you do not know your e-mail password, contact your website administrator to obtain your password.

When you've entered the two fields, click the "Login" button.

NOTE: Session Cookies MUST be enabled. Otherwise you will recieve a login failure.