how to use two ammeters on same circuit in different locations.

Ammeters have to be connected in series with the load and two ammeters connected in series with the same load on the same circuit would show the same amount of current. Ammeter's internal resistance is so low that it would normally be disregarded. Likewise, a clamp-on ammeter on the same circuit would measure equal amount of current, so you should assume both will have the same reading regardless of location. If they do not, you've probably clamped them  on different circuits or one of them is on just one leg of a circuit where the other one is measuring the whole of the circuit.

So, I'm not exactly sure which practical situation would require two ammeters on the same circuit because they should both show the same current. Maybe you can elaborate on your particular task?