Looking through the rangefinder (the right one), focus with the focusing gear at the right-hand side on the camera top.
When the distance ring is at "°" position, the gear is lock.
To release this lock, depress the ° lock lever (circled in the fig.), and at the same time rotate the gear, otherwise turn the distance ring on the lens.

When using 28mm or 35mm lens, locate the subject through the left finder, and then focus through the right one.