If your replacement part did not come with a flash lens, you must transfer it from your old panel.

Use a spudger or your finger to firmly press on the lens from the outward-facing side (the side you can usually see on the phone) of the glass panel until it loosens from its recess.

Remove the lens and transfer it onto the back side of the replacement panel.

Make sure to orient the flash lens properly such that the fresnel rings are stacked vertically.