Try to go outside in the sun. Let the sun at your back, point the light meter in front of you. That should read around 1/125@f/11 or 1/125@f/16 on a sunny day, with DIN 21.
PROBABLY you must align the DIN number with the needle (or the "stripe" which the needle indicates). So for the case in your picture, you should turn the crown until (let's say you have a DIN 21° film, corresponding normally to ISO 100) the 21 is aligned to the white stripe indicated by the needle.
This will give you an exposure index (the red arrow on the right pointing to a red figure) and a series of exposure couples on the lower part of the ring.
So if you go outside on a sunny day, and you have a DIN 21° film, and you align the 21 with the stripe indicated by the needle, you should see e.g. EV 14* and the following exposure couples:
* Edited from the original EV 15. The exposure couples above correspond to EV 14 at 21° DIN.