If your pet wants food (if your food meter goes down) just press F. If your health meter goes down (if your food meter is down all the way every 3 seconds your health meter goes down) press H. You may notice your happiness meter in the top left corner of the screen, it is connected to your food meter if your happiness goes down so does the appearance of your pet. You can play with your pet by clicking the park button on the right of the screen. Your pet can work by clicking the other button on the right of the screen. If you find yourself in the park or mine just press ESC to get back to the main level. And finally the Dev commands, well you will have to figure that out on your own. Good luck!
Note that this game still is an alpha and the game is still in heavy development.