Note: All Excel protection is relatively weak. It is useful to stop casual users but it is not for top secret information.
At a file level you can put a password on so that it is required before the spreadsheet is opened. So when someone wants to open the file, they first must enter the correct password. This means that only people who know the password can open/ change the file.
To follow along go to 19.1
You do this when you save the file, so either when you first save it, or (if you want to add a password to an existing file when you do a Save As.
As shown below, there is a ‘Tools’ button when you are saving and the one you want is the ‘General Options’.
When you click on this you get the following options:
All the options work by either entering your password into the appropriate block or ticking the appropriate box. If you enter a password it will ask you to confirm it when you press OK.
If you enter a password only in the ‘Password to Open’ (1) section, then the file can only be opened if the user knows the password, but they will be able to make changes to it. .
If you also complete Password to Modify (2) and/ or Read only Recommended (3) the file will act slightly differently.
So if you are happy that the person who knows the open password can also make changes then you would only enter a password into the Password to Open section.