Easiest way to setup a voltage telemetry? (OpenCC3D, X8R, Fatshark 600tvl)

I've been googling about and give up. There just seem to be a bunch of different options and maybe that's what's so confusing to my tiny brain. This is my first FPV racing quad and I somehow managed to get it all assembled by hodge podging guides from all over the internet.

Now I'm trying to figure out either a simple OSD of the voltage reading for my goggles or a way to get my taranis to beep when the voltage drops.

Please help! Thanks