You’ll need the calibration plug to access the h menu, its all done through the dash screen. You will also need to do a valve calibration if its not had autosteer on before.
For the teensy firmware i use it from the boards repo, its the aio v5 canbius modified sketch and i use arduino ide to flash it
Youll need to go into serial monitor and select brand 2 for nh and also select P for panda gps.
Have you looked here.
The calibration procedure is also there i think. The WAS and SPOOL calibration can be a bugger to get started