How to apply the Display Assembly Adhesive

While you can use a liquid or gel-type glue, the pre-cut adhesive available here and elsewhere are recommended, as they are made to fit exactly on your phone and will provide a modicum of water resistance when applied properly.

If you read carefully on the iPhone 13 Screen Replacement guide, you'll find that Step 26 specifically mentions replacing the adhesive and gives a link to a page showing you how. Here's the adhesive page.

iPhone Display Adhesive Replacement - iFixit Repair Guide

You haven't mentioned what repair you're doing that requires you to remove the screen, but typically you'll install the adhesive just before you reconnect the display. Depending on the battery connector, you may need to plug it in as you install the adhesive so the backing sheet will lay flat on the phone as you press down the edges; if you do, be sure to unplug it again before proceeding to connect the screen.

If you haven't installed screen adhesive before, I might suggest you buy a couple of sheets of the precut adhesive. That stuff is not forgiving at all, so if it doesn't go on correctly the first time, you don't get a second chance; if you're like me you'll just end up with a tangled ball of glue. Having a spare on hand would mean you won't have to wait for a reorder to arrive before you can put your phone back together.