Please , really need help

hello everyone
i have a project to make communication between arduino and HMI weintek 8070iH(i use Easybuilder8000 software), i use RS485 2w to interface that. i want to send string data from HMI to arduino and show in serial monitor in arduino(HMI master and Arduino slave). i have a problem , i cant send data from hmi to arduino, can anyone help me please?

Post a link to the datasheet for the device you want your Arduino to communicate with.

Post the Arduino program that you have been trying and tell us exactly what happens when you run it.

A diagram showing how everything is connected would also be a great help. See this Simple Image Guide