While walking across the bridge that connects the bell ringer with the bell, look down off the bridge at the side of the building. You'll see a window ledge you can jump down to. Carefully position yourself and jump down to the window ledge. Shoot out the window and quickly dispatch any of the ice monsters you may encounter. There is a lever in this room that drops all the ladders when you pull it. Using the ladders, make your way all the way up to the top of the bell tower. At the top you will find another lever that has a picture of a bell on the wall behind it. Pull that lever and the bell will rise up. I think you can figure the rest from here.