3 Ways to Lock Windows 10 Computer
Way 1: Lock computer via the user icon in Start Menu.
Open Start Menu, click the user icon and choose Lock in the list.
Way 2: Lock computer through Ctrl+Alt+Del options.
Press Ctrl, Alt and Del at the same time, and then select Lock from the options.
Way 3: Lock computer in Screen Saver Settings.
Step 1: Type lock computer in the search box on taskbar and choose Lock the computer when I leave it alone for a period of time.
Step 2: In the Screen Saver Settings dialog, choose On resume, display logon screen and hit OK.
Referred from: https://www.isunshare.com/windows-10/3-ways-to-lock-windows-10-computer.html