Pokemon sun aether paradise [closed]

Your question is quite vague. If you've just accessed the lower levels after your first encounter with Faba:

From this walkthrough:

After you have defeated him, Faba will grant you access to the lower floors. When Gladion asks you if you’re ready to go, reply with “no”. Head south until you find the friendly Aether Foundation Employee who offers to heal your Pokémon. Now head back and travel down to the lower labs with Gladion.

You are unable to go back until you have cleared the lower level section. Continue forward.

If instead you are referring to the second Faba encounter, near the end of Aether Paradise:

Guzma and Lusamine make a swift exit after the battle so you can relax for a bit now. Leave the mansion and Lillie will be waiting outside for you. Gladion hands Lillie a Moon Flute (Pokémon Sun) / Sun Flute (Pokémon Moon). He also hands you a Master Ball.

There’s not much more to do on Aether Paradise right now so it’s about time that you head over to Poni Island. Simply retrace your steps by heading south, taking the elevator down to B1F: Docks and speak to Gladion.

Additional source (spoilers)