Willer by vogue 2004 built in sound system

Can any one tell me where are the input / feed say you want a radio how is it connected to the caravan system?

As all we seem to have are the bank of four switches and two outlets, one each corner of the lounge with speck on plugs that plug in with with four wires. I think these are speaker connections, please help I am a bit stumped.

I just need to no how I supply music into the system?

thank you