The film counting window opens by pulling down the lever at the camera back (circled in the figure).
Wind the film until the number "1" on the leading paper comes in the window.

With depressing the button in the center of the frame counter, turn the counter in the direction of the arrow till it stops.
Lastly, close the cover for the film counting window.

Attention : Do not forget to close the cover for the film counting window lest the film is exposed throught it.