I don't think you can connect the subwoofer without using the center channel speaker/ control pod. It probably won't even turn on without it.
The black mini plug is the input for the center & sub. You would need a cable with a stereo 3.5mm jack at one end and two RCA plugs at the other end. One of these will connect to the sub out on the receiver. If you connect the wrong one you will hear bass from the center speaker.