How to connect GCS to Vehicle

Hi, I am new at UAV/FPV and am wondering how to connect the GCS (e.g. QGroundControl) to the vehicle such that the GCS can control the vehicle. I am planning on using a TARANIS X9D with R9M/R9 but have not found any information on how one connects the GCS to the vehicle such that commands can be sent from the GCS. Is there some way of connecting the GCS to the R9M using the serial or smart link port ? Or is this only supported by some telemetry systems and if so what might those be.

Thanks and apologies if these questions are already answered somewhere else.

You must have tellemetry unit on your quad/plane and one to your ground station

If the 2 tellemetry unit communicate then when you will open the qground control it will connect automatically

This is with a Android phone

Some of this is out of date but it will be helpful anyway.
Common options:
Sik radios (915/433 Mhz)