There is very little to know about the meter knob.
First, as you will know, it offers both incident and reflected light metering modes. To change between the two you have to slide the diffuser blind in front of or away from the metering cell, completely covering or uncovering the cell respectively.
To move the blind you have to unlock it by pushing the little catch aside.
You set film sensitivity by turning the slotted disc on top of the meter. This works best inserting a coin in the slots. Turn until the required ASA or DIN value is opposite the appropriate white triangular marker.
The meter displays results using a simple meter needle. Make sure when reading it that it coincides visually with its reflection in the mirrored surface below.
The needle points to black and white "zones", above which EV values are marked. You set these EV values to the lens, and then select any of the resulting aperture-shutterspeed combinations available.
The needle must be checked for correct "calibration" now and again. You do that by covering the cell completely, making sure that there is no light reaching it. The meter needle should then point to the small white line at the left of the scale. Should it not do that, you need a small screwdriver to turn the tiny screw sunk into the side of the meter housing (not the rim) carefully, until the needle does point to the white line.