Dell XPS 14 (L401X, Late 2010) - Manual (Page 18)

18 Memory Module(s)
3 Slide the memory module firmly into the memory-module connector at a
45-degree angle, and press the memory module down until it clicks into
place. If you do not hear the click, remove the memory module and
reinstall it.
NOTE: If the memory module is not installed properly, the computer may not
boot.
4 Align the tabs on the memory-module cover with the slots on the base
cover and snap the memory-module cover into place.
5 Tighten the two captive screws that secure the memory-module cover to
the base cover.
6 Replace the battery (see "Replacing the Battery" on page 14).
7 Connect the AC adapter to your computer and an electrical outlet.
8 Turn on the computer.
As the computer boots, it detects the additional memory and automatically
updates the system configuration information.
To confirm the amount of memory installed in the computer:
1 tab 2 notch
3 memory-module connector
3
1
2