Locking your screen prevents other people from accessing your computer while you are away from it. All of your applications and work remain open while the screen is locked, and the screensaver is displayed.
To lock your screen, you need to add an Action Buttons panel plugin to your panel.
Right-click on your panel, choose Add New Item and select Action Buttons.
Choose the action Lock.
This will add a button for locking the screen to your panel. You can also define a keyboard shortcut for locking the screen. In order to do this, choose Shortcuts.
→ → , and you will find the options under the tabTo unlock the screen, move the mouse or press a key. Then, type your password and press Enter.