In order to install a 3rd party certificate, follow instructions below:
1. Click the Generate certificate request button:
2. Generate New Certificate dialog opens:
3. Fill in the required details and click Save
4. Click Copy to copy the request, which will be sent to certificate authority.
5. Request a return certificate in the following format: Apache, with the private, public and intermediate CA all in one file, with extension .pem. (.cer and .pfxare also fine)
6. Once you receive the SSL certificate from the certificate authority, click the Import public key button on the SSL/TLS tab page.
7. Browse to the certificate file containing the public key and click Open. Click OK to save the settings.