@linchee - You might want to start by turning a light on and off using an Uno and the Serial blueprint plugin here that so graciously provided. Turning on and off a light is like Hello World in programming. There are several examples on this thread of the C code you need and the blueprint layouts. There is also one post from showing how to run a servo with code. As far as using blueprints themselves - Unreal has a channel with tons of videos explaining them.