It’s not as simple as replacing an iPhone screen. I believe most (if not all) android phones use only adhesive to keep the screen attached. Google your phone and there will probably be a link to YouTube for a tutorial on how to do it.
Don’t hold the button in the back for 25 seconds. Hold it for like 5 or 10 seconds with the lid open and both AirPods in. Disconnect from charger and look in Bluetooth menu afte white light starts flashing Update (03/15/2018): Do they have warranty?