Bit of an ice puzzle, but honestly it is really easy. Just go down on the first ice square you can get to, go to the right and grab the Calcium, then slide to the other side of the rocks and go down the stairs.
Take the left ice square down, go around the rocks and on the second one tile ice square slide up then go around to the left and slide to the right. Go down the stairs at the top.
Slightly harder of an ice puzzle this time. Go down the left tile to hit a rock straight away, then slide right, down, left, down, right, up, left, up, left, down, left, up, right and up. Down the stairs.
Slight maze. If you have Strength, go down and move the boulder. You want it so that it is in one of the tiles either directly north or south of the ice square, then enter the square in the unblocked side and you will be blocked from going right across. Slide right, collect the Full Heal then simply go through the maze and down.
Take the middle tile of the upper three ice tiles and go down on it, then from there go down, right, up, left, down, right and up to get onto the main island. This is Regigigas and if you have Regirock, Regice and Registeel in your party and you press A on it, it will attack!
(Taken From Gamefaqs)
All credits goes to Drayano (www.gamefaqs.com)