The game automatically saves your progress. You don't need to worry about it.

If you wish to start the game again, or if someone else in the house wants to play the game, you can create a new player. Go to the main menu and click the "Change Player" button to bring up the Change Player screen. From this screen you can add new players, change player names, and delete players. Every player will have their own progress tracked.

Next: Buying the Full Version