Kind of an unanswerable question without knowing HOW you wired your truck.
But it might be pretty easy to have a functioning ammeter. All the LOAD stuff goes on one side of the ammeter. And the other side is just a direct connection to battery.
To oversimplify it….
If you used some sort of fuse panel, you need to feed it from that load side of the ammeter.
But a better way to answer your question is to have you describe your current state.
