Solution
To install an SSL certificate:
1. Click on the Install an SSL Certificate and Setup the Domain link in the SSL/TLS menu.
2. Enter the domain, user name, and IP address for the certificate in the Domain, User, and IP Address fields.
3. Click on the Fetch button to paste the .key and .crt files for the domain into the available display spaces, if they are currently on your server. Otherwise, copy and paste the .key and .crt files into the available display areas.
4. Paste the ca bundle for the certificate in the bottom display area, if required.
5. Click on the Do it button.