The big bulkhead connector has the female terminals. They are released with a small flat tool. I've used cotter pins, small screw drivers and finally bought the correct tool.

Again borrowed from the Civilian Jeep forum..
This shows the locking tab that must be released.


This shows the tool in action:


I have the multi-tool shown in that picture. Disadvantage over a single prong tool is that the extra prongs sometimes get in the way. My '67 bulkhead is a little different but similar enough I think the double prong gets in the way with the bulkead.

These came from Basic Wiring 101 page 1.
If you go there and have a slow connection, just know that site has lots of ads etc. No-script is one way to minimize the extra graphic downloads.
CJ wiring is a little different than SJs and our mopars so you can skip the CJ specific stuff. He mentions Packard 59 connectors for the bulkheads. I don't know if that applies to any of our mopars, but if you see slightly larger terminals, then that's what they are.

Nacho suggested an alternative to butt connector splice is crimping two wires onto the ammeters ring terminal. This avoids extra connections. Done properly, it will look like this.

At least on my '67 Barracuda, that's how Chrysler joined the voltage regulator wire to the Ignition Run wire at the ballast resistor.
To do this will require an ring terminal (for the ammeter) with large enough wire capacity. If you have trouble doing this well, then butt connector is better. Basically, use whatever method you can accomplish that provides good a connection. Every connection is location for problems, so generally the strategy is to minimize connections. But one bad connection is worse than two good ones.