(1) Select the Save As command on the File menu, and enter the filename in the Save As dialog box that pops up, as shown in the figure:
(2) In the dialog box, select General Options in Tools, as shown in the figure:
(3), enter the password in the "Save Options" dialog box that pops up. Excel provides two levels of protection, and if you set a password to modify permissions, you will need to enter a password to modify permissions even if you open the file, as shown in the figure:
(4), click "OK" button, in the Pop-up Password confirmation dialog box re-enter the password, and then click the "Confirm" button to save the completion of the file encryption work.
Select the Options command on the Tools menu, as shown in the figure:
In the Options dialog box that pops up, select the Security tab to set the password on open and modify password for the current workbook, and then click OK when the settings are complete, as shown in the following illustration:
When you reopen the file, you require a password, and if the password is incorrect, the file will not open.