Go into the room where there is an ice slide after pulling the lever. Go on the left side and go toward the end going down on your screen. You will then enter another room. Go to one of the three and find a thing that looks like a steering wheel on the floor and examine it. Bring it to a pipe that is missing a waterwheel and examine that, too. Then go to another room until you find a room that is completely made of ice. Find the lever there and pull it. I think you can pretty much get the rest.

Oh there will be another lever in the waterfall on the left, I think so pull it and get all five of those little fountains to spit water out and have Hermione freeze them with Glacius.