Choosing where you go when you sign in
By default, you see your Start screen every time you sign in to your PC, but you can go to the desktop or the Apps view instead if you want.

To boot to the desktop instead of Start
  • Open Taskbar and Navigation properties by swiping in from the right edge of the screen, tapping Search (or if you're using a mouse, pointing to the upper-right corner of the screen, moving the mouse pointer down, and then clicking Search), entering Taskbar in the search box, and then tapping or clicking Taskbar and Navigation in the results.
  • Tap or click the Navigation tab, then tap or click the When I sign in or close all apps on a screen, go to the desktop instead of Start check box. Then tap or click OK.

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Full article from Microsoft Corporation - Personalize your PC - Microsoft Windows