Remember to put on your safety glasses if you have not already. Glass, and shattered glass especially, can be dangerous if proper eye protection is not worn.

Briefly run the heat gun on a low setting around the outside edge of the screen to warm up the adhesive keeping the phone in place.

Keep heat gun on a low setting, and keep the point you are heating moving. Do not hold the heat gun in one spot for long.

Work an iFixit opening tool under the lip of the screen and pry upwards carefully.

Once you are able to work the screen up around the edge of the device, pull the ribbon cable out of the phone through the thin slot at the bottom of the phone.