To install Plesk on a number of servers, you may want to set up a mirror of the official Plesk update server (http://autoinstall.plesk.com) inside your network so as not to download the distribution files through the Internet each time, and then install Plesk as described in the Installing Plesk section below.
If you do not want to set up a mirror, you can skip the Setting Up Mirrors section and go on to the Installing Plesk section.