FD3S stereo cable mystery...

[<--rYaN-->]

hi i bought my fd3s and the door speakers were apparently disconnected. i want to reconnect them and i dont know how, theres a cable coming out of the back of my aftermarket stereo and its not plugged into anything, so if someone could tell me or have a look behind their head unit for me and tell me where this goes then it will be amazingly appreciated!!!!
ryan