What are the steps to connect the Pixhawk to Auvidea J120 board using a telemetry cable?

I’m looking to get a connection between my Pixhawk and Onboard GPU using telemetry. However, it doesn’t seem to be connecting for some reason. I followed the instructions given on this page – https://ardupilot.org/dev/docs/companion-computer-nvidia-tx2.html

I’d appreciate it if someone could note down the steps to get a connection from scratch.

** I do not need any information regarding flashing the firmware, for I’ve already done that. My only requirement is to observe a connection when the telemetry cable is connected to the GPU board, the same way it occurs when connected via USB.