Most of you will already know this, but for newcomers, here is the essence of how to calibrate the Open Gamma Detector. If you have your complete device with a scintillator, you only need a sample that has well-known gamma-ray energies. You can use these to calibrate the bin axis and then export the calibration.

In this video I'm using two tiny LYSO scintillators as a Lu-176 source. This isotope has two very well-known gamma peaks that are ideal for a very simple linear calibration.