Sony PCG-F420 Primary User Manual page 83

Wait until the computer cools down. Then unscrew the screw at the
bottom of your computer. Loosen the screw with an appropriate
screwdriver.
Touch a metal object (such as the connector panel on the back of your
computer) to discharge static electricity.
Remove the memory module.
Tighten the screw on the bottom of the computer.
✍
Follow steps 1 to 4 of "To remove a memory module."
Remove the memory module from its packaging.