SUPER-INCREDBLY simple IMHO.
Plug one unit into a wall socket.
Attach Ethernet cable from router to it.
Done on one end.
Plug the other unit into a wall socket elsewhere oin the house.
Attach an Ethernet cable to it.
Attach other end of Ethernet to Mac.
At this point you can turn off your WiFi and test it out.
If it’s not autodetecting, which my Macs did with no issue, go into System Preferences > Network and make sure the Ethernet interface is enabled and running.
One caveat: If you have a MacBook, you may need an adapter, e.g., USB-to-Ethernet.