Gently insert the top edges of the palmrest under the screen hinges, then lay it down onto the rest of the laptop.

Carefully slide the touchpad ribbon cable back under the metal frame and latch it back to the motherboard. (I found it easiest to do with a spudger or blunt tweezers on plastic edges of the ribbon cable.)

Your fingerprint sensor's ribbon cable should already be pre-bent to match grooves in the metal frame below it. Try to position in it that groove as you reattach the palmrest.

Gently press down around the edges of the palmrest to snap it back into the body of the laptop.