Pin 15 and Pin 16 are being used for the LED-Backlight:
Pin 15 is the positive terminal.
Pin 16 is the negative terminal.
Both pins must be connected to a voltage source TOGETHER with a
resistor, to limit the current for the Backlight. The current should not
exceed 30mA, but you should try 15mA to 20mA first. The forward-voltage
for the LED-Backlight is somewhere between 3,0V and 3,6V.
Pin 3 (VEE) is used for the contrast(translation?) of the display and
should be connected to a slider of a 10k-potentiometer. The ends of this
potentiometer are to be connected to Ground (VSS) and 5V-Supply (VDD).
Hope this helps ...