Motion Capture LPE Communication

Hello,
I am very new to px4 and mavlink, and I am trying to build a motion capture positioning system for a drone.

I created a motion capture system from scratch and I am wondering how I can communicate that information to the drone via mavlink.

The software is written in matlab and I can export the data in any format, I just need to know how to talk to the pixhawk to give it current position.

I see that I need to use ATT_POS_MOCAP message I just dont know what exactly that is doing.
https://dev.px4.io/v1.9.0/en/ros/external_position_estimation.html

Can someone direct me to some info that might help me achieve this?

Thanks!
Greg