Apple Mac mini (Mid 2011) - Manual (Page 42)

42 Chapter 3 Boost Your Memory
Step 3: Remove the bottom cover.
Lay your Mac mini upside down on a soft cloth or towel, and then rotate the bottom
cover counterclockwise to the unlocked position.
Unlocked
Press on the cover to pop up the opposite side, and then remove the cover.
Press here
Lift here