Continue peeling away the backing from the adhesive, gently pressing the adhesive into place from the bottom of your iPhone to the top.

If you correctly aligned the lower edge of the adhesive, the side and top edges will fall perfectly into place. If the adhesive is misaligned, remove it and start over with fresh adhesive.

If you don't have another set of adhesive strips handy, it's okay to temporarily put your iPhone back together and use it normally without any adhesive. Just keep in mind that your iPhone's water resistance will be compromised until you replace the adhesive.