Once you’ve added text and values in your worksheet and you’ve included a chart or two, you need to ensure that your workbook is saved by clicking the Save button on the Quick Access toolbar (or by pressing Ctrl+S). You can also protect the workbook or individual worksheets in your workbook so that only those people whom you want to allow access to your Excel data will be able to do that.
Click the Review tab.
Click Protect Sheet.
The Protect Sheet dialog box opens.
Select the check boxes adjacent to the protection options you want to apply.