Click on the pie when it appears to be fully cooked,(the crust will become a nice brown color when it's ready) click and drag to move things, and press buttons for different things. The blue circle button is for sugar, the yellow rectangle button is to get a pie(unmade), the red diamond button is for fruits, and the green square with a customer icon is to serve the pie. The number below the pie type is your money. Chef Scratchy will tell you the rest. Try giving customers the wrong pie and see what happens!
Thanks to waffleshamster for the original project Pi(e) maker beta.