Connect the Nano board to computer via the USB cable, and open the Arduino IDE. Select the board as Nano and the correct port, upload the code. Then check whether three levels work normally by pressing the button. The fan should rotate slowly for the first pressing, a little faster for the second, and then much faster for the third. Then stop at fourth pressing.

Besides, this fan is a thermally controlled one - it will spin in the strongest mode automatically when the temperature reaches 34 ℃ (threshold adjustable in the code)