I am very new to assembly language and I have been instructed to make the brightness of a bright white LED to vary according to the brightness of the room that the LED is in, the brightness of the room will be detected by a light dependant resistor and the PICKIT3 must be used to program this scenario. My question is how exactly do you make the output voltage coming out of the pickit vary? Is there some simple assembly instruction that can do this? And how exactly can I enable the input from the light dependent resistor to be understood by the PicKit? Any help will be much appreciated

Your code will be the intermediary between the two.
Do you have a list of commands for the processor(s) involved?
I'll see if I can help.

I'm looking at the manual, now: http://ww1.microchip.com/downloads/en/DeviceDoc/PICkit_3_User_Guide_51795A.pdf

and this one:
http://ww1.microchip.com/downloads/en/DeviceDoc/33014J.pdf

And this project to use the LED as a light sensor:
http://www.micro-examples.com/public/microex-navig/doc/096-led-light-sensor
It is in C, but looks translatable.