How to use DO pin of ldr module to turn off lcd ?

I have ldr module with 4 pins

  1. Vin
  2. Gnd
  3. AO
  4. DO

I want to know how can i take advantage of DO suppose i want to turn on lcd display when light falls on the ldr sensor!

See in attached image of my ldr module, I have noticed when light falls on ldr sensor the Green led with DO written next to it lights up

‘If’ it is this module, DO would go to an input pin, ex: pin 2 on the Arduino, then do a digitalRead on that pin.

Adjust the trigger point potentiometer on the module for the level you need.

digitalRead works, but i think i get inverse result 0 for when light falls on sensor and 1 for when its dark.

You sometimes have to invert your logic thinking when it comes to writing software ;).

if(myVariable == HIGH);
if(myVariable == LOW);

I was thinking i am getting wrong result

That module uses an LM393 comparator which has an open collector output that switches LOW when active. A 10k pullup resistor holds the output HIGH until activation pulls it LOW, so logic is "reversed", HIGH for OFF, LOW for ON.
Very common in digital logic, that's why most all MCUs have internal selectable PULLUP resistors.
Pseudo code:

if(light_detector == HIGH)
   backlight = true; // ON
   backlight = false; // OFF