You may start the service at the certain time using graphical user interface or command line options. We recommend using GUI until you get more experience: http://wiki.eltima.com/user-guides/application-as-service/schedule-tab.html
Please, select your service in the "Services list" and click "Edit" in Main menu, then go to "Advanced" and make sure that in "Upon program exit" you haven't specified "Shutdown the service". In order to ensure your service will be launched again once it is failed, please, go to Main menu -> Edit -> Recovery and choose Restart the service in Computer's response in case of service failure.
Please, check the Event Viewer, there might be details of service failure and send them to us for investigation.