The AHRS/Calibrarion feature allows you to generate and test calibration code for Magnetometer and Gyroscope sensors connected to your NRF51 based Bluefruit LE device.
Connect to your Bluefruit board using the calibration app and choose either Magnetometer or Gyroscope mode depending on what sensor you'll be calibrating.
Keep rotating slowly in a sphere until you get decent coefficients (this can be a bit tricky and takes some trial and error to get right).
Once you have data, note it down as shown in the USB example above.
Next download this sketch, and plug the mag co-efficient values into it:
Once the values are plugged in, upload the sketch to your Bluefruit board.
Connect to your Bluefruit board and run the '3D Visualisation' mode on the app. You will see a 3D model of a bunny. Readings sent from your Bluefruit board should allow you to rotate the model by rotating your board.