I mean, when you start the save, the balls are always at the top right of the machine. Slowly push numpad 0 to get them out.

If you meant the net in the bottom, you can press numpad 0 again, since the machine carries 3 balls, but if you used up all three balls, you can either use the physgun to move the balls back where ever you want, or you could reload the save.

how do i get the ball out?