How can I enter the lighthouse?

Hint 1 of 6:

How do I unlock the front door?

Hint 2 of 6:

Have you tried knocking?

Hint 3 of 6:

Nobody ever answers the door.

Hint 4 of 6:

Look around, and see what you can find.

Hint 5 of 6:

Sometimes, you must stoop to conquer.

Hint 6 of 6:

Under one of the items on the porch is a key.