Do you have NPrinting Server, or just the Designer? If only the Designer, you will need to leave the program open in order for the schedules to run.
If you have the server, here is how you can load a schedule to run as a Windows service: How to Configure QlikView NPrinting 16 Service
Note: I would always recommend adding a folder rather than adding a file. If you add a folder, any new .nsq that appears in that directory will have its schedule accounted for. Otherwise you will have to stop the service, manually add the .nsq and then restart the service.