Use the point of a spudger to lift the ambient light sensor and proximity sensor out of their recess in the display assembly.

There is a small, square plastic and metal holder for the proximity sensor. This holder is essential for the proximity sensor to function correctly.

If replacing the proximity sensor make sure that the holder remains adhered to the back of the display. If it comes off with the old proximity sensor, remove it from the old sensor and use a tiny bit of adhesive to re-attach it to the back of the display.