My ice maker is not working I need to shut it down

Without a brand and model, difficult to tell. Many units have an on/off switch in the freezer compartment above the ice cube tray. There most likely is a water shut off behind the refrigerator, pull it out and shut off the water.

Many ice makers shut off by just raising the bar that goes across the unit that detects when tray is full. It's a wire that goes up and down. DrTom4444