Sorry, I misunderstood exactly what is happening, and there are two people with same tractor.
Apparently you have nothing except the 3pt, and you want to add a rear valve,and use what JD calls a PB port, which probably comes directly from the pump to the side of the tractor..
I believe there are some ports on the side of your tractor that you have to add your kit to. If you followed the directions, it should work.
You have to provide a flow path for the fluid from the pump to the tank, and by adding the kit, and valve assembly, correctly, you will achieve that .
Your JD manual should indicate the correct ports for the kit.
I am thinking you will have a hose from the side of the tractor to the new valve, and a hose from the valve to the side of the tractor.
Does the new valve use two or three hoses to connect it to the tractor?