In preparation for launch, fill your bottle part-way with water.
Grab a friend and find a wide open space to launch your rocket. Have your friend press the cork into the bottle and flip it so the nose cone is pointing upwards and away from you. The bottle should gently rest in one hand and the pump should be firmly held in the other.
When your friend and rocket are ready, start pumping! The pressure will start to build and after a few seconds, your rocket will blast off into the air!