OK there should be a FP-USB connection point on your motherboard. (Is that the 8-pin thing your talking about?)
seeing that you have only 4 wires for your usb means you only have 1 usb port on the front
OK the wires should have basic labels on them.
should look something like
VCC
USB2-
USB2+
GND
What is your motherboard? How are the 8-pins arranged on the motherboard? (2 columns, 4 rows?)
mine are arranged 2,4 and I have 2 USB ports. It should hook up just like the order I posted above.
Mine has another wire called "Shield" on 1 of the USB port wires