I really don't understand the problems you are having.
Just connect the 4-pin wafers as shown in the schematic and also on the PCB layout with the same pin numbers on both boards.
There are four pins to connect which are: +12V, circuit ground (negative terminal of the power source), AF-signal and shield for the AF-signal.
Connector numbers are Y1 for the master and Y1A for the slave. Pins1 on each connect to +12V, pins2 connect the AF-signal, pin3 and 4 connect to ground and ground shield.
I drew in the AF-signal in red and the shield in blue. Check the pin numbers. They are identical - master has the identifier Y1 and the slave has the identifier Y1A. Pin numbers have to be connected to the same pin numbers on both wafers. 1-1, 2-2 etc.
Boncuk