Remove the screen.

If you replaced your screen, check the front-facing camera hole and the sensor cutout on your replacement screen, and remove any remaining liners.

Check your phone if the proximity sensor's rubber gasket is missing—it might be stuck to the back of your old screen. Replace it if necessary.

This is a good point to test your phone before sealing it up. Temporarily connect your screen, power on your phone, and make sure it works as expected. Before continuing with reassembly, power off your phone.

Follow this guide to replace the screen adhesive.

If you're installing a new screen, follow this guide to calibrate the fingerprint sensor.