HELP Where to plug cd changer in???

[A6SE]

I have bought a CD changer that sits in the boot. I have a Concert cd radio and my manual says it can control the changer. I ordered this cable from ebay http://cgi.ebay.co.uk/ws/eBayISAPI.d...=STRK:MEWNX:IT but cannot seem to find where it should plug in. There is also a sat nav disc drive in the boot (CD type not DVD) that works, should the blue fitting plug into the sa nav somewhere or in the back of the radio. I have removed the radio and there are no free spaces to plug it it, the only place I can plug it in is if I remove the top black plug (long fitting) everything still works when I remove this, and plug in the smaller half the length blue plug - but the changer doesnt power up. Should the wires go into the larger black plug thats already there??? HELP!

[A6SE]

Ha ha, Frekin sorted it - popped out the 8 wires from the back of the blue iso plug, reinserted into the black block on the back of the radio but still did'nt frekin work then, don't know why earthed the changer to the body of the car (as it's sat inside metal holder in the boot) and hey presto, bloody magic Cos I'd had the unit on the front seat to test it, that was what had caused all the bloody problems