Dell 23.8" OptiPlex 7410 All-in-One Desktop Computer (Gray) - Manual (Page 44)

Steps
1. Align the notch on the memory module with the tab on the memory-module slot
2. Slide the memory module firmly into the slot at an angle and press down on the memory module down until it clicks into
place.
NOTE: If you do not hear the click, remove the memory module and reinstall it again.
NOTE: Repeat steps 1 to 2 for each memory module to be installed on your computer.
3. Close the DIMM door and press it into place, securing it.
Next steps
1. Install the back cover .
2. Install the stand .
3. Follow the procedure in After working inside your computer .
44 Removing and installing Customer Replaceable Units (CRUs)