Navigate to your webmail login page with one of the following links. Be sure to replace example.com with your actual domain name:
example.com/webmail
webmail.example.com
You will see the Webmail Login page.
Enter your full email address, and password, then click the Login button.
You will log into Webmail and see three options. Click the Horde link to log in.
You should then see the Horde interface, and can begin using webmail.