Why do they freeze hockey pucks?

Answer 1

So it moves better and is slick on the ice.

While freezing the puck may help a little with movement on the ice, the actual purpose for freezing is to reduce the bounce. Warm pucks have a surprising amount of bounce that will affect face-off drops, and players' overall ability to handle the puck.

Answer 2

Pucks are kept in a freezer until needed. There is usually a freezer in the time/scorekeepers box, or one of the penalty boxes.

Answer 3

Quite literally, place it in your freezer (or outside if the temperature is below freezing). Frozen pucks have far less "bounce", and should always be frozen before use in a game.