A split photo is composed of 2 different photos merged together. The split wil be made by 4 vertical interleaved bars
Now, only 2 stripes (out of 4) of your photo are impressed on the film. Turn the film-advancing wheel slowly until you move forward the film of 1 centimiter (you should hear between 12 and 14 clicks).
Shoot the first photo.
This will impress the other half of the film.
Now, shoot another photo.