Hello,

What you need to do is:

• SSH to your server
• Then go to this folder here: /etc/apache2/sites-enabled/
• There you need to find the SSL Vhost for your website
• Open the file and look for these lines: SSLCertificateFile and SSLCertificateKeyFile
• In the copy the location of the files and then in those files you need to add your new SSL certificate: so in the SSLCertificateKeyFile file add the new private key and in the SSLCertificateFile add your SSL certificate followed by the CA bundle
• After that run a config test for your Apache service: apachectl -t
• If you get Syntax OK you can restart you Apache service: systemctl restart apache2

Let me know how it goes!
Regards,
Bobby