When you press the arrow keys or action, this input is sent to the main player.
If you press left or right then the camera turns 90 degrees in that direction. If you press up or down or the action button then the appropriate motion is sent to the player object, and the game updates. Game rules do not run when you turn on the spot.
Sometimes you will want to have several player entities on screen at once. Don't worry, input gets sent to all of them :)
Sometimes you will want several different types of objects to be able to receive input. Let's call them Player1,Player2, Player3. You can define player as follows in the legend section
Player = Player1 or Player2 or Player3
and then three of those entity types will receive input from the player.