1, click the Office Button, in the Pop-up Drop-down box, select "Prepare"-"encrypted document" command.
2, in the pop-up "Encrypted document" dialog box, enter the password, click the "OK" button.
3, pop-up "Confirm Password" dialog box, in the "Reenter Password" text box again enter the password just set, click the "OK" button to complete the encryption.
4. Close the presentation, when we reopen the presentation, the Password dialog box pops up, and you need to enter the password you just set and click OK to open the presentation.