@cagkana9f5cd873f5b8188e469

Simply follow the tutorial that outlines the installation on Apache:
https://www.digitalocean.com/community/tutorials/how-to-install-an-ssl-certificate-from-a-commercial-certificate-authority#apache

But your end configuration would look something like this:

<VirtualHost *:443>
  ServerName www.xxx.com
  ServerAlias xxx.com

  SSLEngine on
  SSLCertificateFile /path/to/certificate.crt
  SSLCertificateKeyFile /path/to/certificate.key
  SSLCACertificateFile /path/to/intermediate.crt

  DocumentRoot /var/www/xxx.com/public_html
  ErrorLog /var/www/xxx.com/error.log
  CustomLog /var/www/xxx.com/requests.log combined
</VirtualHost>

<VirtualHost *:80>
  ServerName www.xxx.com
  ServerAlias xxx.com
  Redirect permanent / https://www.xxx.com/
</VirtualHost>