Siemens PLC S7 1200

Hi All,

i am currently trying to program a Siemens PLC S7 1200 with the RS485 IO.
basically i am wanting to connect this to the Cerbo, a third party specialist sensor will be connected to the s7 1200 PLC’s RS485 which works on RTU Modbus, so i will be pulling data from the sensor into node red.

my struggle here is with TIA Portal 19 ( first time user!) i have tried a few different ways an i cannot get the PLC to be seen via ModBus on the Cerbo.

any help would be massively appreciated