BETA65S

Getting started (with OpenTX radio)

Some official documentation here and here (binding)

Create new model on Transmitter - Use internal multimode module in FrSky mode
Bind RX with TX (official docs have some info, basically like the USB stick, there is a bind button on the quad's main PCB)
Download and install Betaflight Configurator here (windows).
Connect USB (without battery)
Open Betaflight Configurator
In Receiver section verify moving sticks moves the correct bar, if throttle is wrong, change TERA or whatnot to AETR and click Save button
See which bar moves when you toggle the switch you've setup in the TX for arming, keep a note of it.
In Modes section, under Arm, click the button for range and toggle your switch, it should select that input automatically, if not pick it from the dropdown. You should see the little tick mark move as you toggle the switch, move the selection to the right side and only covering the general area around the tick mark. Click save and reboot. Go back to this section after reconnecting, toggling the arm switch should cause the Arm section to highlight.
In Tuning section set the 0.7 values to 0.5 (three of them, one for roll, pitch, and yaw), save and reboot.
Unplug USB
Make sure TX is on with throttle down and arming off
Plug in charged battery
Arm
Give a bit of throttle and the props should spin.