wireless audio + amplifier: help me locate possible audio input

[chafporte]

Hi, This is a 900mhz audio mono wireless analog receptor combined with a 10w amplifier. I would like to be able to input wired mono audio in the circuit (ie bypass all the radio parts of the circuit). The potentiometer at the top left in on/off + volume. The top right is channel tuning. black and red are optional battery supply. Blue red white at the top are going to a led to help the tuning. The other blue white red are filtered (tweeter+medium/boomer) signals sent to the speakers. I don't know much about electronic circuit, but I should be able to do the soldereing if someone can tell me where.
Thanks for your help