1. Navigate to the Utilities folder. (within the Applications folder). Open the Keychain Access Utility application.
2. From the application's main menu, select Keychain Access, Preferences... Check the box next to "Show Status in Menu Bar". Close the Window and the Keychain Access application.
3. You will now see an small LOCK icon on the right-side of your applications window. (Near Date & Time and Spotlight.) Click on the lock icon and select "Lock Screen".
4. The screen will immediately switch to your screen saver, but you will be prompted for your password in order to get back to the desktop.
