HP Deskpro EN Supplementary Manual page 40

7. Press out on both latches of the DIMM socket at the same
time 1. This releases the module and partially pushes it out
of the socket.
8. Lift the module from the socket.
9. To install a memory module, reverse the procedure. Push
the module down 2 into the socket, ensuring that it is fully
inserted and properly seated 3.
Inserting a Memory Module
When the computer starts up, it will recognize the system
memory upgrade and automatically reconfigure the system.
Guide to Features & Upgrades 3-15