You will have to check first through the finder or even directly trhough the filter where you get the desired effect. Then you mount the filter on the lens making sure you put in the same position. It will help if you put some marks in the outer ring to help you determine the exact position.
This applies also to TLR. Rollei made a polarizer with a scale on the outer ring (rolleipol), so you will determine the desired effect with the viewing lens , remember the number on the scale aligned with the index mark and then you'll put the filter on the taking lens and made sure the number in the scale was aligned with the index mark