Start the normal server and make sure it starts automatically when you start it. If it doesn't start automatically then set the options in the server config to make it start.
Open a command prompt window in the ServerConfig folder. The service executable ffsrvice.exe is in this folder.
Install the service using the command "FFSrvice /i". You will not see any message but you can confirm that it's running by looking at the Windows task manager.
Now the server service will start with Windows and run in the background.
To uninstall the service use the command "FFSrvice /u"