Yup read the user manual ....
OK, I got that said now for some hints
Hopefully you know and have used the battery selector switch. The batteries will be within about a 2 foot circle of the switches. If the battery switch is under the helm ( I don't know for sure) the batteries are probably in front of the hlm somewhere in, behind, or under a panel in the starboard side storage compartment behind the helm'
If the battery switch is aft by the transom, the batteries are close to that spot. You may have removable drop in boxes in a aft locker. The bins come out and there will be things in the lower space.
Your battery switch has positions like 1, OFF, 2, BOTH.
If you set the switch to 1 (Battery 1), battery 2 will never charge. Same goes for selecting 2 all the time. Battery 1 will never charge.
Some devices may be directly connected to a battery and even if the switch is set to OFF (which it should be when not operating the boat), a device can drain a battery.
When you select a battery or BOTH, try to do do so with the motor off. You can select a different battery option with the motor running but never switch to or past the OFF position.