An important task before you use your EDTracker is to calibrate it. Failure to calibrate the device can result in inaccurate responses and "drift" over time, where the output of the device slowly creeps in a direction (typically left or right) separate to the position of your head - which can obviously be quite disconcerting!
The process for calibrating your device uses a graphical user interface that you can run on your PC in order to monitor and set up your device.
A handy PDF guide that covers both flashing and calibration can be found in the downloads section. The process is different for MPU-6050 and MPU-9150 equipped devices, so please ensure you choose and follow the correct user guide.
Alternatively, you can follow the video below for a step-by-step guide to device calibration...