Calibrating the Harmony N380 System:
1. Turn system power on
2. Pedal the bicycle lightly through the entire calibration procedure
3. Press and hold the "mode" button (the silver/chrome button on the shifter) until the rear hub begins shifting (5-7 seconds typically), then release the button.
4. Continue pedalling lightly while the system shifts from "low" to "high" ratio multiple times and completes the calibration.
Here is a link to the complete manual for your reference: