This is unlocked early in the game. After certain developments you will see wounded Jack lying on the beach. To the right of him is a boat, and to the right of the boat is a mast of a ship buried in the sand. After you acquire Magical Compass, Spyglass and Cutlass you will have to proceed to the right into the jungle with 2 parrots watching you, where you will pick up Hook Rope and Torn Shirt. After you go back to the beach you will use the Hook Rope on the net swinging from the mast. Get ready. A red target circle will start moving across it from southeast to northwest and it will turn green when it's centered on the net. That's when you have to throw it with the
button. If you miss it the first time don't wait but hit Start button and exit the game. Restart the game and select Continue (it will load into the parrot screen), and try again.