To install a new screen:

If any adhesive is still on the front shell, use the flat end of a spudger and tweezers to scrape it up and remove it.

Apply isopropyl alcohol to any adhesive residue on the front shell and wipe it away with a microfiber or lint-free cloth.

If you're reusing your screen, use the same cleaning process to remove all the old adhesive from it.

If your new screen comes with adhesive pre-installed, remove the plastic liners and press the screen into place on the front shell to secure it.

If your new screen doesn't have adhesive, use strips of strong double-sided tape such as Tesa Tape to secure the screen to the front shell.