POWER LED hook up

Question

I have a p4vxasd2+ V 5.0 MotherBoard. It has a (Power SW) which i found the proper slot. The (POWER LED) hook up from my tower has three pronx. wiring diagram does not help. Does anyone know how to make this hook up (POWER LED) What does it mean. There is a fan system which has three pronx.Thanks for your help