How to Add Password Protection in Excel
When a password is added to a workbook, only authorized users with the password can view or modify it.
Enter passwords in the password text boxes as desired.
You can enter just one or both passwords, depending on the type of protection you want for the workbook. Passwords are case-sensitive.
Check the Always create backup box to save a copy without a password incase the password is forgotten.
Type a secure password that can't easily be guessed by other users, and be sure to write down your password in a safe location.
The workbook is now password protected. To change or remove a password, repeat the workbook protection steps and simply change or delete the password in the General Options dialog box.