The 4in1 ESC already has the PDB built in so all you need to do is connect the 4 ESC cables (labled 1-4) from the ESC to your APM outputs.
You dont need to use the PDB inlcuded with the arducopter, as you will connect the power module directly to the ESC and battery
The plugs will depend on the the motor connections, to keep it simple I would suggest you look at the arducopter motor diagrams. On the ESC you will see that each set of 3 motor connectors has a number M1 (A1,B1,C1) M2 (A2,B2,C2) etc… Connect your motors according the the APM diagram.
Now you will need to connect the small wires (S1-S4) from the ESC to your APM board. This is the same where S1 corresponds to M1, S2 corresponds to M2 etc… So S1 will connect to the motor output 1 on the APM board. S2 to output 2 etc.
Also if you are looking to change the settings/program your ESC details can be found in the 4in1 ESC programming manual.
Hope that explains it