[Free][Windows only] UE4Duino 2 - Arduino (COM port) communication

Well, the discussions here will help you a lot.
You can connect to several Arduinos, as long as you know the port numbers. Just create a different variable for each connection and never forget to close them before the end of your game.
I don’t know about any tutorials, but the images that come with the plugin might help you. And the brief explanation in the first post of this thread.