The drawing is a bit crude but should help.
At the bike, under the seat, I connected the trailer 12 volt line, black wire, to the running lights line on the output side of the trailer isolator, green wire. This will only supply 12v to the trailer when the running lights are on. In the trailer I cut the black wire and connected it to the input of the breakaway box, black wire. I connected the output of the breakaway box, blue wire, to the black wire that was cut earlier. This is the side that feeds the interior light which I also connected to the charge port. The white wire of the breakaway box was connected to the white ground wire in the trailer. Note, I put 5 amp inline fuses in the black wire feeding the trailer, under the seat, and the blue 12v line from the battery box.
With this setup the bikes battery is isolated from the trailer interior light and charge port so you can’t run down the bikes battery by leaving the interior light on. It also allows you to have light and charging abilities when the trailer is disconnected from the bike.
Let me know if there are any questions.......
Greg