You start of course by creating fixed microwave radiation. Then you measure the absorbance spectrum for different applied magnetic field values. This will determine the different g-tensor values.
Afterwards, you slowly change the sample orientation, by rotation over a small angle. Then you do the magnetic field sweep again, giving new g-values for this specific, new angle. you keep doing this for new angles until you’ve covered most angles (and due to symmetry you sometimes apparently only need to do until 90°).