As soon as you get in the fire side of Hailfire Peaks, look to the left. There should be a big square stone. On top of it is a big crack. Make sure you are on top of it and that Chilly Billy is mad and is throwing fireballs at you. He will blow up the big square stone, revealing a flight pad. Go on it and fly to the mountain. There should be a platform there. Go on it, making sure you have some Ice Eggs. Enter the door in front of you.