There are two ways to really do this.
You can either pay apple $600 to fix it.
Or let’s say you are starting a repair company for iPhones.
Then you could buy something like JC1000s or similar
and use an application such as 3uTools to find the original screen’s serial number.
Then you can burn it to your new screen with the JC
Tutorial Video Here:
https://bit.ly/jcifixit