Instructions
Use all three Lunar Landers, which are circular platforms on top of the three different buildings. Run up the staircases in the first building so that you're on the roof. Locate the Lunar Lander's control panel on the roof -- it looks likes a monitor on a pedestal in the middle of the area. Approach the control panel and push the button that appears on your screen. The Lunar Lander arrives. Step into it, then push the button indicated on your screen. The Lander transports you to the next building. Repeat this process until you've used all three Landers, which activates the rocket's control panel.
Return to the main building and go up the staircase to where the power switch is located; you have already flipped the power switch earlier in the game, so don't flip it again. Instead, approach the rocket control panel near the switch. Press the button that appears on your screen to launch the rocket.
Run outside to where the rocket was located. A hidden door that was originally covered by the rocket is now visible. Go inside; the Pack-a-Punch machine is against the wall.