When you go to Tall, Tall Mountain, keep going up the mountain until you reach the waterfall with the black brick box in it and head to the piece of land on the bottom. Its better if you use luigi because of his spins after the backwards summersault. After you do that, when you see the angry cloud just sprint accross it so yu dont get blown away. If done correctly you will reach a bunch of curved coins. The place where they intersect with the wall is where you will jump in to. After that you will go to a secret slide that is VERY TRICKY so be careful. After you reach the end, there going to be a hole where you are supposed to jump in so after you jump in you will somehow go to the side of the big terrain of the big blue tough bomb-omb and the star will be there!