After you find the PiPhone prototype, you get to the Prune HQ.
Talk to the brainiacs to get a access card. You can use it to get up to the Skyloft with the elevator.
Get yourself the PiPhone with the voucher from the brainiacs.
Unlike normal walkthroughs, in Nice Game Hints you can select just the puzzle you want hints for. Here are listed the puzzles for "First visit" in Leisure Suit Larry - Wet Dreams Don't Dry. The guide you choose only contains information about that puzzle, reducing possible spoilers for other puzzles.