Summary
For Signing out, Locking, Shutting down, and Restarting your machine through menus and with shortcuts in Windows 10.
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Overview
On Windows 10, the Sign Out and Power Options are slightly different than what one might be accustomed to in Windows 7.
Process
For Signing Out and Locking:
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Access the Start Menu via the Windows Icon in the lower left corner.

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Right-click on your Account Icon and select the option that says Sign out or Lock, depending on the action you're taking.

You can also press ctrl+alt+del on your keyboard and select the Sign out option. Holding the Windows Key+L will lock your computer.
For Shutting Down and Restarting:
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Access the Start Menu via the Windows Icon in the lower left corner.

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Click on the Power Button and select Shut down or Restart, depending on the action you're performing.

You can also press ctrl+alt+del on your keyboard and select the Shut down or Restart options.
For additional information, check these categories in the Knowledge Base:
More Windows 10 guides can be found here.