How do you convert a 4 input NOR gate into multiple 2 input NOR gate?

you will need 2 two input AND gates to do this. connect the output of the first to one input of the second. you now have a three input AND gate.

just remember when calculating timing that 2 inputs of the 3 have twice the gate delay of the remaining input, thus the output will have skew and possibly glitches. if timing is critical or glitching can't be tolerated it may be best to use an actual three input AND instead of kludging one.