A CDN is usually an external service, with data replication. But you can also have a CDN on the same server. This will improve performance a little because assets (images, CSS, and JS) will be served statically.
The trick is to have cdn.example.org in addition to example.org
- If you are using https, you need to add this to your certificate, which is easy with Let's Encrypt
- Create a new sub-domain with your DNS provider (usually your domain registrar)
- to assign two domains to your site (via the web server admin panel in ClearOS)
- Set these sub-domain name (http and https) in Content Delivery Networks at tiki-admin.php?page=performance
- Visit the main domain.