Turn the laptop upside down. Release plastic tabs holding the case top to the case bottom. Use caution because some cables limit the range of motion.

Peeking in from the side, disconnect the red, white, blue and black cable by carefully pulling the connector out of the socket.

Move and rotate the case bottom out of the way, exposing the CPU and CPU fan assembly. See second photo.

Some cables between the case halves remain connected. Take care not to break them or pull them out of their connectors.