You know the 4 pins on the molex connectors? The red one supplies +5v, and the black one next to it is the ground. You have to figure out a way to get the wires of the fan hooked up to those wires from the PSU. If the fan connector is a 4-pin style, you can push the female connectors out and then put them back in the other slots, that would probably be the easiest way.