First, you choose a wheel to attack. Then, if the blow connects, a d6 is rolled and the result is used to determine the actual wound location. Outer wheel is used for swings and inner wheel is used for thrusts. Start counting from top and go clockwise. That’s it. If armour deflects the blow completely, there’s no need to consult the wound tables.
Also notice that the number of the wheels allows easy d6 randomisation on ranged attacks. Or 1d3 randomisation, if you’re close enough to aim “high” or “low”. We’ve also added an armpit location to simulate the weak point in many ancient armour.