AMP instructions vs Ammeter help!

What they are showing in the drawing is a VOLT meter It goes from power to ground

An AMMETER (or amp meter same thing) measures CURRENT and is wired in series.

The "rules" for ammeter is, only the battery hooks to one terminal, and the generator/ alternator output and all loads hook to the other side, except of course the main big starter circuit

Then, if turning on the lights shows "charge" just reversed the wires on the two posts

BE CAREFUL. The original wiring is NOT FUSED in that circuit. Unhook the battery ground when messing with this!!