How to Connect 3 arduino with modbus RTU using RS485 interfacing?

please [HELP]

i need connect 3 arduino interfacing RS485 with modbus RTU,

I will control :

Arduino 1 : MASTER
Arduino 2 : Slaves 1
Arduino 3 : Slaves 2

Arduino2 (slaves 1) have 2 potensio to control 2 led in Arduino 3(slaves 2)

Thank you...