wiring for second battery on 29udql5 xlr

[Remaxin]

i have a 2016 xlr nitro 29udql5 toy hauler and it has two compartments for batteries one on each side. The dealer only put one battery in on the drivers side and I would like to install/ hook up the second one that is on the passengers side (were the solar on the side is) but wondering if any one has wired a second battery on this model, has schematics for it or know which post to connect the second battery too

[boondocking]

Take a volt meter and check if there is 12 volts on the cables on the passenger side compartment. If there is then connect the positive battery terminal to the +12v cable and the negative battery terminal to the -12v cable.
If there is no 12v then sorry, can't help any further.