Password Protect Workbook. Double-click on the Excel document to open it up. Click on the File tab at the top of the screen. Select Info from the menu that covers the left side of the window.Click on the Protect Workbook button in the Permissions area of the screen.ouble-click on the Excel document to open it up. Click on the File tab at the top of the screen. Select Info from the menu that covers the left side of the window. Click on the Protect Workbook button in the Permissions area of the screen.