Dell Precision 7920 Owner's Manual page 49

b Lift the coin-cell battery out of the system board.
Installing the coin cell battery
1 Place the coin-cell battery into its slot on the system board.
2 Press the coin-cell battery with positive (+) side facing up until the release latch springs back into place and secures it to the system
board.
3 To install:
a air shroud
b graphical processing unit (GPU)
c side cover
4 Follow the procedure in After working inside your computer.
Removing and installing components 49