This document provides instructions on how to install and configure Varnish as a web accelerator in front of Apache on Ubuntu. It describes downloading and installing Varnish from its repositories, configuring Apache to listen on a different port than the default 80 so Varnish can listen on 80, editing the Varnish configuration files to set parameters and define Apache as the backend, and restarting the services so traffic is routed through Varnish. It also provides a command to check Varnish caching status and metrics.