This will depend on the type of mouthguard you've acquired. Patients who don't wear custom-made mouthguards will have to fit theirs by first submerging them in a pot of boiling water for no longer than 20 seconds to soften them up. Please remember to use a spoon or any other utensil that allows you to fish out the mouthguard without getting burned. Right away, submerge the trays in cold water for 3 seconds tops so they don't remain uncomfortably hot as you bite down on each set. You should prioritize fitting the mouthguards to your front teeth' position. You can also help hold the guard's position with your tongue. Finally, hold this position for 30 to 45 seconds to finish the fitting process.