How Do I Charge, and Maintain 2 New 6 Volt Batteries???

Treat two 6v GC batteries as one big 12v battery and get yourself a good three stage charger. Don't forget that 6v CG batteries should NOT be filled to the ring, like a car battery would. If you fill them that high, they will spill over into the battery box. Cover the plates with electrolyte, but don't over do it!