I have used the HK Dipoter Sight Tool alot, and find it very easy. Still, seems that both follow the same principle of use, and the US one is cheaper....
Just remove the adjustment tool from the back of the screwdriver, insert the adjustment tool's two claws into the notches in the sight, and insert the screwdriver. Adjust the POI up, by rotating the sight counter clockwise, adjust POI down by rotating clockwise. The drum should rotate smoothly/loosely when you have done it right, it it is not in place it will turn with noticable clicks to the next position.
To adjust windage, loosen the set screw/clamping screw 1/4 turn, then adjust POI left by turning adjustment screw clockwise. Adjust POI to the right, by turning the adjustment screw counter clockwise. When done, tighten set/clamping screw. Before adjusting, remember to take up any play/slack in the adjustment screw before loosening the set/clamping screw.
Always make sure that the set/clamping screw is tight, before shooting, to avoid change in POI during shooting.