Lenovo ThinkCentre A55 8705 Hardware Replacement Manual page 22

10. Go to "Completing the installation" on page 26.
14
Hardware Replacement Guide
a. Position the heat sink on the microprocessor socket and then position the
clamp on the plastic retention bracket. Pivot the handle 1 to clamp the
heat sink to the plastic retention bracket.
b. Position the heat sink on the plastic retention bracket so that the four
screws are aligned with the posts on the system board. Tighten the four
screws 1 to secure the heat sink and fan assembly to the system board.
9. Reconnect the heat sink and the fan assembly cable to the system board.