1, Install two AAA batteries into battery cassette before covering its cover. 2,Plug one finger into rubber hole of the Oximeter(it is best to plug the finger thoroughly)before releasing the clamp with the nail upwards. 3,Press button on the front panel. 4,Don’t tremble your finger when the Oximeter is working. Your body is not recommended on moving status. 5,Press the button on the front panel,if we want change display direction 6,Read relevant datum from display screen 7, The instrument has the function of sleep. 8,Please replace new batteries when OLED indicates the batteries are in low power.