voltmeter or multimeter or whatever its called

Ok... I have this new mini-itx motherboard and I'm making one of those NES computers everyone has. Now, I know nothing about electronics and I kind of want to learn but lack the motivation.

I'm trying to figure out which wires go to which pin for the power buttons. I know which pins are for power (from the manual) but I do not know which wires on the NES buttons are which.

I do not really know how to understand the readings on this meter. I'm pretty sure I am using it correctly, though (red to one end and black to the opposite). Do I just match the readings of the wires to the readings on the two power button pins?

 

All i can tell is that the red ones are positive and black ones are negative. Now this means that red ones are connected to the terminals with lower potential of the battery and black ones to the upper potential of the battery.