This page only appears on Windows. Registering as a service on linux needs to be done manually. see Running on linux
MailScheduler is designed to run as a service. To enable or disable the service, select the option in the Installer.
If you have selected to not run MailScheduler as a service but would like to change this option, or vice versa, you can run the same installer you used for the latest upgrade / installation and select the option you would like.