Rob.
Always best to keep the batteries fully charged. While they should be fully charged when they leave the factory, and retailer, this is in reality, a pipe dream.
Your pd9245 is a good charger. The member you bought it from simply did not want to cut the AC cord off to hardwire it to his system.
Hook one battery cable in series from the + of 6v battery 1, to - of 6v battery 2, this is now a 12v battery.
Run DC output - cable from PD9245 to - of battery 1 and the + to battery 2.
You will have to provide the cables from PD to battery as it does not come with them. You will likely need an Allen key to tighten the screws down on the stranded wire.
Plug in the remote/wizard into the plug on side of PD9245
After connected to the batteries, plug it into the wall and the PD shold seek 14.4v with upto 45 amps.
Your newly acquired batteries will likely only take this for a few moments until amps start tapering, but it should hold 14.4v for 4 hours before reverting to 13.6, and eventually 13.2v. You will likely be able to hear the batteries bubbling, perhaps the occassional gurgle. NO worries.
You can also force it to 13.6v by holding the button on wizard/pendant for a few seconds, or 13.2v when holding for a few more seconds. The rate at which the green light blinks indicates the 'stage' it is in which indicates the voltage it seeks. The lower the voltage the less amps will flow, so if the only copper wire you have laying around is quite thin, then I would recommend forcing 13.6, or 13.2 quickly after plugging it in.
Even if you do not have thick DC cables at this point, the batteries should not be able to accept big currents for long where thinner copper would be indanger of overheating as the batteries should not be able to accept 45 amps for very long. Only if they were very depleted would they be able to suck up 40+ amps for a while and thicker copper necessary, at this point.
But you should get them full while you plan the rest of your system. At 13.2v, you can leave the PD plugged in as long as you want, or unplug it. The little green light on the wizard will stay on even if unplugged from wall outlet.
Whenb fully charged, you can either remove the PD, unplug it, ot leave it plugged in at 13.2/ storage mode. When in storage mode, every 18 hours, it will bump voltage back upto 14.4v for 15 minutes to mix things up. PD calls this an 'Equalization' stage, but really it is a destratification stage. The Bubbling/gassing caused by 14.4v will destratify the electrolyte.
If you choose to unhook the PD all together after fully charging, hook it up again in 30 days to top off the batteries again as they will self discharge. Upto 15% per month at 75F.