How do you get through ice gym on Pokemon Crystal?

To reach Pryce, start to the left of the left hand Pokeball Column near the entrance of the gym. Then simply go up, right, down, left, up and right and you will be in front of Pryce. You will have to battle some of the trainers before you reach him.

As for "getting through" the gym, if you mean beating Pryce - simple. Use an electric or grass Pokemon for Seel/Dewgong, as they are dual ice/water types (preferably electric as grass is weak to ice), and a fire type ONLY for Piloswine. Alternatively, go and level up some more. Pryce is really not very hard to beat.