Sending data to RS485 device using Grove RS485

Hi.
I’m trying to send data to Modbus device ( SAE FW-5-Gate) (https://www.sae-it.com/en/products/telecontrol/fw-5-gate.html).
This is my client device. He asked me to send the data to specific address. I’m using arduino to send the temperature & humidity data over the grove to the RS485 port on FW-5.

How do I set the modbus address?

During testing, I’ve send successfully the data to the PC using RS485-USB convertor.