you have electric fans...
well... there are a bunch of different ways to do it.
run it from a 12v constant to a switch
or pull power from a 12v switched
or a combo of both
or get a whole set up that allows the fans to operate like they are supposed to at certain temps. Could be a bit more involved but it is "technically" the right way.
just google it, you'll find more info than you'll know what to do with on the first page