Drag Max onto the car. 2 arrows will appear at the front and the back of the car. If you click and drag the front arrow, you'll move the car forward. If you drag the back one, you'll move it back. Once a car is parked drag Max to the key booth in the middle of the screen. Then click on the highlighted spot to hand the key there. If a guest wants to take his/her car back, go to the booth first, take the highlighted key, go to the car and drive it to the exit.