Battery charging

[Dennis & Stephanie Littrell <dlittrel@northernnet.com>]

I'm sorry, folks, I really am. I've looked everywhere and I can't find any
information on how to charge the twin 6-volt batteries in place using an
external source.(Dad: "I can't figure out how to charge the B's batteries."
13-year-old son: "Why don't you just start it up and drive it for a while?")
Which cables go where, please?

TIA,
Dennis
'73 B Roadster "Shirley Valentine"