Beckhoff CX9001-1001 and CX9000-N031

Hi, I'm working with Beckhoff CX9001-1001 and CX9000-N031. I want to have 2x RS485 modbus rtu, how N031 must be configured in System Menager Twincat for this use? witch lib i musy use in PLC Control?

You will need

TwinCAT PLC Modbus RTU + licence

For details on how to configure it get

Documentation

You need to know if you want your CX to be master or slave.
You will find all relevant examples inside the documentation chm file.

Thanks for info about lib!
my CX will be master, how N031 must be declared in system menager? I must add "appened device... -> Miscellaneous->serial com port" or system find N031 by himself?