Facing the unit from the front, it will be the line on the right. Turn the valve clockwise until it stops. This will turn off the water supply to the softener. Contact the installer. For leaks when the unit is new, contact your installer first.
Most leaks are the result of installer problems.
SmartWater authorized installers provide a 30-day warranty on their installation. Contact the installer. The installer is responsible for the tubing and the connections bringing supply water to the inlet of the valve on the softener and taking the soft water from the outlet of the valve on the softener to the house. The installer is also responsible for transformer wiring connections and power supply.