You can use external bus bars, or you can use the cables shown below and connect the cables directly to the chargeverter and the battery.
EG4 Chargeverter Adapter Cable - Better Connections Improve Your Solar Power System!
@cshurtz I ended up going with bussbars in the BossBox, and then made a cable to hook from the bussbar into one of the batteries. The power should distribute from there to the other two batteries