You play as the Doctor, you role is to be the doctor that you want. So as a player you explore the possibilities of the mechanics and you discover different meaning too your actions. A way to play An Apple a Day is to find the more "ending" possible. I would say the way to play this game is by trying to understand your action as a doctor and understanding the effect of your choices.
CONTROL : AWSD or Arrows
You can consider the game finish when you found seven "ending" . The game is all about choices, it is normal to feel a little confused about the actions you make at first. The actions all make sense after a few play.