RS485/COM port
Use an RS485 cable cable plugged into the inverter port labelled "RS485" which is located at the bottom of the inverter.

Steps in SolarAssistant
On the configuration page, select "Felicity Solar T-Rex" as your inverter model.

Select the USB port(s) where you have Felicity Solar inverters connected.

Click connect:

Parallel installations
With Felicity Solar inverters you will need to connect each inverter with its own cable.