This will cover how to assign and use the Flight Mode feature, as well as the additional functionality it unlocks for AS3X. It is also a required to later on set up SAFE.
AR637T Receiver:
https://www.horizonhobby.com/ar637t-6-channel-as3x-telemetry-receiver-spmar637t
Update Cable:
https://www.horizonhobby.com/as3x-programming-cable---usb-interface-spma3065
Update Software:
http://spektrumrc.cachefly.net/apps/spektrum_programmer.html