Funton,
Welcome to the Stovebolt...great handle! If this is on your '53, the process is pretty straightforward.
The alternator, if it's a three wire SI, or internally regulated unit, will have a small DA plug with two wires, and a large power wire. The large power wire ( BATT) can be connected to the wire from the old BATT terminal on the voltage regulator. This will route power through the ammeter so the system reads as it did before.
The small wire from DA#2 can wrap around and connect right to the large terminal..BATT on the alternator itself.
The other small DA wire marked #1 needs to be connected to a switched source of power. This would be a terminal on the key switch itself. Your key switch should have two switched terminals...either one will work.
The two remaining wires on the old voltage regulator would have been ARM and FIELD (I think). These can be removed or just taped up and left for posterity...they are no longer used.
Be sure to address the other areas when switching to 12 volts. These are things like lamps and voltage reducers for a few critical items. Good luck.
Stuart
