Lightly clean the surface of the two chips highlighted in red on the first picture.

Be sure to position the heat sinks correctly before you stick them down, as the adhesive is extremely strong and sensitive to being repositioned.

Stick the two heat sinks down against the top of the two chips highlighted in red on the first picture, being sure the fins are aligned as seen in the second picture.

When reinstalling the optical drive, be sure both the power and SATA cables do not interfere with the heat sink attached closest to their sockets on the motherboard.