Jack, a lot of G'byte motherboards have what amounts to 2 power LED conectors, one a 3 pin connector usually off by itself, the other a two pin connector as part of the Front Panel Header Block.
IH, look for the F_PANEL drawing. Should be around page 15. Use pins 2 and 4 labeled "Message/Power/Sleep LED".
The LED's are polarized. White wires go to the "-" pins. If you get it wrong, just reverse the plug. You will not hurt anything. The switches are not polarized.