At the file level, you can password protect an Excel workbook in two ways: You can determine who can get in and who can save changes.

If you have sensitive data you'd like to keep from prying eyes in a Microsoft Excel file, the easiest way to protect it is with Excel's built-in password tools.

You can add or remove a password from your Excel spreadsheets through the File tab. You'll do it slightly differently on a Mac and PC.

Open the Excel file you want to protect with a password. Click on File -> Info. Now select Protect Workbook. Select Encrypt with Password from the list. Now enter the password. Confirm it once ...

I tried to set a password on it again, but I’m getting the following error: “This workbook contains Excel 4.0 macros or Excel 5.0 modules.