You will need a clamp or a slot screwdriver to pull out the white button located on the top of the valve. Then, use a clamp or your fingers to turn the button. You will see a red line change position on the screen located on the top of the valve. When the red line is perpendicular to the valve, this means the valve is closed. If the line is parallel to the valve, this means the valve is open.
Please note: if the red line does not move position, this means the white button was not pulled out enough.