After connecting your GNSS module to your autopilot, you'll need to set it up using your favorite GCS, QGroundControl or Mission Planner.
To configure your mushroom GNSS module with QgroundControl, go to the Sensors configuration window under Compass and calibrate your compass (both external and autopilot) :
Then, setup the external compass's rotation in case you did not set the GNSS board heading the same way as your autopilot. Do not forget to set your autopilot so that the external compass is used and active.
Calibrate the compass by successively performing the rotations indicated by the images with your camera.
In the window above, select Rotation_None.
For full information concerning the setup of your GNSS board within your machine, refer to your GCS's user manual (QgroundControl / Mission Planner).