You install it like a new system. (well, it is a new system)
Claim the new server. New Claiming Requirement for Windows
You may have to edit all your Plex clients and un-pin/un-favorite the old libraries, then pin the new libraries.
https://support.plex.tv/articles/customizing-the-mobile-apps-2/#reset
https://support.plex.tv/articles/customizing-the-apps/#reset
https://support.plex.tv/articles/customizing-plex-web/#resethome
