Download and run Windows installer from here. Follow the steps in the installer and agree when it asks for administrative privileges. Administrative privileges are required to install Windows service called “R3DS License Server” which will start automatically with Windows.
Installer will detect any previous installation and will run in new installation / reinstallation / upgrade / downgrade mode automatically.
After successful installation the installer will open web interface of the server, where you can see run-time information about the server and find the instructions on how to add license and connect clients.