Run CMServer.exe on the license server with Administrative privileges (right-click on the file and select Run as Administrator). It will display the configuration window.
Select "Windows Service" radiobutton and click the Start button.
Note that if the CMServer is already running as an application you need to terminate it first before restarting it as a Windows Service. You should terminate the server from the File menu of the CMServer window, not using the “X” as the “X” only closes the Viewer application but does not terminate the license application (if you did use the “X”, please open Task Manager and kill the CMServer process)