PC fans are very easy to install this is how you do it

there are on most fans 3 wires black red and yellow that is the 3 pin they are talking about, get a DC adapter 12v atleast 100ma i use one that is 1000ma which is enough power to run 5 computer fans at once.

splice the red and black wires from the fan and do the same to the adaptor and wire up positive to negative if its wrong the fan simply spins the other direction no damage done there is normally a arrow pointing the way the air should flow.

to cut the hole id reccommend using a jigsaw