Boil some water in a kettle and pour it into a bowl/container big enough to dunk the gum shield in
Let the water cool down slightly to around 80 Degrees C (as a rule of thumb, after boiling the water, wait around 1 minute before dunking the gum shield in)
Submerge the mouthguard into the bowl of hot water
Let the mouth guard sit for 30 seconds max
Place the mouth guard into your mouth and use your thumbs and index fingers to press the mouthguard onto your teeth. (IMPORTANT: Do not bite down on the mouthguard as this will damage the pro air ridges), this should take about 5 seconds
Close your mouth (do not bite onto the gum shield), suck all the air and saliva in to create a vacuum and use your tonge to press the inner side of the gum shield onto the inside of your teeth.
Remove the gum shield and run it under cold tap water for around 20 seconds