Write code.
You'd write code to read the LDR. Once that is done you'd write code for the LEDS.
I take it you want to use 4 LED's with all LED'S on with the brightest light and all LED's off with the darkest light with all LED's on. A set of 5 steps. or 20% increments. Then you'd want to measure the light, getting the readings of the brightest and the dimmest readings the LDR will produce. Once you got the LDR High and LOW A:D values, you'd relate the range to 20% increments.