Windows Screen Saver/Lock Setting

Set the Screen Saver Preferences

 Click "Display" from Control Panel

Select the "Screen Saver" tab and set the "Wait" time at a number below 15 minutes

Mannually Lock the Screen

1) Press Control-Alt-Delete then click on "Lock Computer"

OR

2) If you have a "Windows" key on your keyboard, you can select the "Windows" key and the "l" (el) key. It will lock the screen without using any other keys.