Doepfer mc 404 calibration issue

Hello this is my first post in this site. decent forum btw.
i bought mc 404 at really great price, but i have trouble with tuning, scale and vcf offset. How can i calibrate this stuff ?. should i need a voltage meter ?. Service manual says (in german lang.) like ‘’ you should turn p22 trimmer for tuning " and so on but i just cant understant which trimmer is which, there is no some kind of label on it.
Can you please help me guys ?..
check the photo