Take the spool out of supply spool receptacle and insert into that of the take-up spool. Further, slightly turning film rewinding knob, press it and the head of the take-up spool spindle up to the stop. Close the camera back. Put cover on the camera lenses. For convenience purposes, adjust their mounts at the same level.
Contaminated lenses deteriorate pictures sharpness, so it is necessary to keep lenses always clean.
The objective lenses could be wiped from the outside only using a clean cambric or linen cloth or cotton wool, on having breathed on them. Never dismount the camera. Never wipe the plastic parts of the camera and the field lens with alcohol, acetone and other active solvents.