Sending custom messages from QGC

Hello, I am looking to send a custom mavlink message from QGroundControl to my flight controller. I have an xml file with the new messages described however I am unclear of the next step, how these new commands are then integrated into QGC and how to send them to the flight controller. I would like to be able to assign their value using user input from a custom page that’s been made in QGC. Any help or advice would be greatly appreciated.

No one answers much of these questions people ask huh? Guess I shouldnt get my hopes up of my post being replied to.