The communications between the PLC and the VersaMax IO racks will be established in the configuration of the Genius Bus Controller module in the PLC. Each rack must be set with a unique Genius Serial Bus Address (SBA) using the rotary switches on the Genius NIU. In the hardware configuration of the Genius Bus Controller you must set up the amount of inputs, analog inputs, outputs and analog outputs for each VersaMax rack based on the rack's SBA.
Note that VersaMax IO racks that only have discrete inputs and outputs are capable of self-configuring, meaning that you will not need to download to those targets. If the VersaMax IO drops contain analog modules, you will need to download the configuration. Also, I have never been able to download to a Genius NIU using a USB/serial converter. I have always had to do the download using a computer with a real serial port.
If this is a new installation I would advise against using Genius. It is obsolete technology. Use Profinet instead.