To steam a Christmas pudding, you'll need a pudding bowl and a steamer. First, place the pudding mixture into the bowl and cover it tightly with aluminum foil. Then, place the pudding bowl in the steamer and fill the steamer with water. Cover the steamer and heat the water until it is boiling, then reduce the heat to low and let the pudding steam for 2-3 hours. Be sure to check the water level in the steamer every 30 minutes or so and add more as needed.