Where to attach terminating resistor in RS-485 Network?

I have a Master board and Two Slave Boards on a RS-485 network. The are connected to each other by 3 pins. A and B are differential signal and third pin is a ground.

I want to add terminating resistor to one side. On which pins do I wire the terminating resistor?
Also, on which side do I attach this resistor? The board side or the other side?

Thanks!

You attach the terminating resistors between A and B.

You place one terminating resistor at each of the two system extremities.