Unscrew the base water tank and fill with tap water or filtered water. Screw back on the tank and turn the unit upside down for 3 seconds. This will prime the hydro wick so that the humidifier can produce cool mist. Make sure the Puremidifier is plugged in. Next, hold down the power button on the front of the unit for 3 seconds. You will hear the Puremidifier power on. The first mode is the air purifier only.  Quickly push the power button again and you will switch to the humidifier mode and you will see the cool mist begin to flow.  Finally, push the power button quickly for a third time and you will engage the combination mode which will provide both air purification and cool mist.  To turn off the machine simply press and hold the power button for 3 seconds.