Place the mouthpiece in your mouth over the upper teeth. If the mouthpiece is too long, trim the ends back until it fits comfortably.
Boil the water. Place the mouthpiece on a spoon and dip in the water for about 8-9 seconds. Warning: Do not leave the mouthpiece if water longer than 9 seconds or the shape will be distorted. Immediately insert into mouth. Close teeth gently to ensure an even bite. Do not bite hard or you will pierce the mouthpiece. Push the guard into the roof of your mouth by pressing your tongue on it. Keep the mouthpiece in this position for about 1 minute.