Changing the lock screen password on an Apple computer is usually a simple process, and here are the steps based on the macOS system:
Open System Preferences
In the top left corner of the screen, tap the Apple menu ( ) and select "System Preferences".
Open Users & Groups
In System Preferences, find and click "Users & Groups" (which may also be called "Accounts").
Select your user account
In the Users & Groups window, select the user account you want to change the password for from the sidebar. Usually, you'll need to select the account you're currently logged into.
Change your password
Click the "Change Password" button in the right pane.
You may need to enter your current password and then enter a new one. Usually, you'll need to enter your new password twice to confirm.
Set a password hint (optional).
You can also enter a password hint to help you remember your new password. But make sure the prompt doesn't make the password too obvious.
Save your changes
Once the new password is confirmed, click "Change Password" or the corresponding save button to save the changes.
Done
Once you have completed these steps, your Apple computer lock screen password will be updated.
Make sure you remember your new password. If you forget your password, you may need to reset it with your Apple ID or by using recovery mode.
If your PC is using Touch ID, you can also use Touch ID to unlock the screen and approve requests.
If you don't have administrator privileges, you might not be able to change the passwords of some users. In this case, you might need to contact your computer's administrator.
Changing your password is an important security measure, and it's recommended to update your password regularly to protect your data and privacy.