There is an accurate ammeter, how can I use it to scale another ammeter that has not yet been calibrated?

It is necessary to assemble a circuit by connecting a switch in series to the current source, both ammeters and a rheostat. Since the current in series connection will be the same for all elements of the circuit, you can use the readings of the ammeter with the applied scale to apply divisions on the scale of another ammeter (put marks opposite the arrow). Regulate the current strength with a rheostat. Work should be started at the maximum resistance of the rheostat.