Acer Altos R920 Series - Manual (Page 88)

3 System upgrade 70
(2) Position the processor over the socket, matching the two
triangle markers (A) and lining up the processor pins with the
socket (B).
(3) Press the retainer lever down to lock the processor in place.
6 Apply thermal grease.
Apply approximately 0.1 ml of the thermal grease compound to
the top of the processor.
7 Install the heat sink.
(1) Set the heat sink on the processor, aligning the four screws in
the heat sink with the screw sockets in the chassis.