Arduino Communication with Pixhawk ver MAVLink help!

Hello! I am very new to ardupilot and have little experience with it. I have been put in a research position, where the idea is to learn the material as i go. I’m still in college with little experience, s i don’t fully understand a lot of ardupilot and especially mavlink. I have read through both MAVLink and Arduino: step by step and MAVLink Step by Step with little success implementing any useful code. All I want to be able to do is send SET_ATTITUDE_TARGET messages with quaternions from an Arduino using lidars for flight data to the Pixhawk. I have spent days reading through google articles, and any help is greatly appreciated.