Shut down the computer
Unplug the power cable
Remove the laptop battery if applicable
Press and hold the power button for a few seconds to discharge residual power
Open the case or access panel
Locate the CMOS battery on the motherboard
Note the battery type and orientation
Gently release the battery from its holder
Insert the new CMOS battery in the same orientation
Reassemble the case or access panel
Reconnect power and reinstall the main battery if removed
Turn on the computer
Enter BIOS or UEFI settings if needed
Reset the date, time, and any custom BIOS settings
Save changes and exit