Adding Library on Mission Planner

Hello People!

I was always using here just to read but because of a problem, I needed to ask a question.

I am building nickrehm’s F35 vtol aircraft but when the teensy flight controller was functioning normally, it stoped to work out of no reason.
So I wanted to replace it with a regular FC, Pixhawk 2.4.8. But for tricopter quadplane configuration, there is only front two motors are considered to tilt. But in my case, rear motors will tilt and because of that problem, FC is helping to crash instead of stabilizing the plane which is completely natural because of the only one available configuration.

I found a library which enables to work with two rear motors and I want to upload it to the Mission Planner but I couldn’t figure out how to upload a library which is totally my lack of understanding these kind of things.

I hope there is someone who can help me out with this issue. Additionally I am open for other suggestions.

Thank You,
Abdullah