Omfg, this is easy to answer... I bet you got a very old sword, First off... You need to beat the tower of gods, then get all triforce chards, then complete the triforce, and then, when you completed the triforce, you must return to hyrule, you should be able to go to the place of the master sword, grab it, and the huge knights will let their huge sword fall, but you survive, now you will get a short battle with some little knights, when you defeated them, you can NOT smash the barrier yet, you must get Makar, or Medly (dont know what her name is but i mean the bird girl) get these two, and get medly to the earth temple, you beat the dungeon and tada, you get a little bit power in your sword, now get makar to the wind temple near windfall island, and then, beat that dungeon, and your sword is full of power, go back to hyrule, and you are able to smash the invicible wall, good luck beating ganon now
Thats all i can say.