I've found over the years that the best way of doing documentation is to just write it directly into the tooltips, that way people can get information about a parameter quickly by just hovering over it, so all parameters of VRIK and its calibrator have been tooltipped.
About the calibrator, in the "VRIK (Calibration)" scene, there is an example script for the calibration on the "VRIK Calibration Controller" gameobject. It has declared variable VRIKCalibrator.Settings, that contains all the data and references you'd need for the calibration and references to the head, body and other trackers. If you have that filled in, you can just call the static method VRIKCalibrator.Calibrate():
VRIKCalibrator.Calibrate(ik, settings, headTracker, bodyTracker, leftHandTracker, rightHandTracker, leftFootTracker, rightFootTracker);
...which will do the rest.
So to get started with calibration, I'd suggest you make a copy of the VRIKCalibrationController.cs script, replace the input part "if (Input.GetKeyDown(KeyCode.C/D/S))" with however you wish the calibration to be called and you should be ready to go.