How do you protect an Excel file?
Rajesh Pathak
You can follow below steps.
  1. Select File > Info.
  2. Select the Protect Workbook box and choose Encrypt with Password.
  3. Enter a password in the Password box, and then select OK.
  4. Confirm the password in the Reenter Password box, and then select OK.
Source: https://support.microsoft.com/en-us/office/protect-an-excel-file-7359d4ae-7213-4ac2-b058-f75e9311b599

Also visit
Homepage​​​
ME EXCEL TRAINING​​​