I am on the point in the game, needle point island or something, where..

That's just a sidequest, don't worry about it. As for getting on the ghost ship, go to I think it's called Diamond Step Isle, and use the hookshot to get to the hole on top. Once inside, the cave looks like the one inside needle point island, except it has cauldrons in it. Use the cauldrons to teleport through the cave. Choose the right cauldron though, or you'll end up at the start again, the same will happen if the wallmasters catch you. Get to the treasure chest and open it to find the ghost ship chart. Use it to find the ghost ship at night and get upon it (If you try getting on it without the chart then it will disappear) by going up to it. Drop down to the ground and defeat all the enemies to make a ladder appear. Take the ladder up to the chamber with the Triforce Chart inside it. Have it deciphered by Tingle for 395 rupees (Ripoff) and then go the area and find the piece of the triforce there.

First you need the Ghost Ship Chart, if you don't have that - go to Diamond Steppe Island (from Outset Island, sail northwest) and complete the dungeon there. Once you have the Chart, when it's night - look at it and it'll tell you what Island the Ghost Ship is at depending on how much of the moon is showing. So Teleport and/or Sail there before morning - once you beat all of the enemies inside the Ship you'll get a Triforce Chart!