Dell OptiPlex 360 (Late 2008) - Manual (Page 104)

104 Power Supply
6 Press down on the release button on the floor of the computer chassis, and
slide the power supply toward the front of the computer by approximately
one inch.
7 Lift the power supply up and out of the computer.
Replacing the Power Supply in the Mini Tower Computer
NOTE: This procedure assumes that you have completed the removal procedure
first.
1 Slide the power supply into place at the back of the computer chassis.
1 release button 2 power supply
3 screws (4) 4 AC power connector
1 2 3
4