I'm stuck in the game "The Legend Of Zelda: A Link To The Past". What do I do? (question #2)?

I have just recently asked the question of how to get certain items in this game, and have learned that I will have to go to the dark world. I have known only one way to get to the dark world, which is through the mountain. The next part I need to kow is how do I get off the mountain, while staying in the dark world? Or is there another way to the dark world? And if there is, where is it?