In order to log in securely to WHM, cPanel, and webmail, you will need an SSL Certificate. You can purchase a signed certificate from an SSL certificate provider with the name of your choice; for example, secure.primarydomain.com or login.primarydomain.com. To install and manage the service certificate,

1. Log in to WHM.
2. Click on Service Configuration.
   
3. Click Manage Service SSL Certificates.
   
4. For the cPanel/WHM/Webmail Service, click Install new Certificate under Actions.

   Note: When you purchased the certificate, you received three files. Please ensure you have all three files before continuing.

5. Paste the .crt file in the space provided, and click Browse. The subdomain name will be displayed. 
6. Paste the content of the .key and the CA bundle files in the spaces provided.
7. Scroll to the top of the page and click Submit.
8. In the Server Configuration section, click Tweak Settings.
   
9. Click the Redirection tab.

   Note: Make sure the Always redirect to SSL option is set to On.

10. Click Save.