LoRa encryption

I’ve just started experimenting with the RFM9W Lora Radio breakout, which seems to work pretty well (although I’ve only done basic stuff so far).
In the product documentation there is reference to an encryption key, and in the packet with the radio, there is a paper label printed with what looks a little like a MAC address. Could you please tell me if these are related, and suggest where I can find more information on how to use that facility?