Incubators generally have some sort of method to adjust the thermostat. Last time I checked, chicken egg incubators like Hovabators use a wafer thermostat that has a knob on a threaded shaft somewhere on top. The shaft runs into the incubator to the thermostat. Turning the knob changes the setting.
If this does not help, post details of your incubator and thermostat. There wasn't much to go on in the post above.