Open the Excel file
Click File
Click Info
Click Protect Workbook
Click Encrypt with Password
Enter the password
Re-enter the password
Click OK
Save the file
Close and reopen the file to confirm the password is required
Open the Excel file
Click File
Click Info
Click Protect Workbook
Click Encrypt with Password
Enter the password
Re-enter the password
Click OK
Save the file
Close and reopen the file to confirm the password is required