Each time that you log in to your device running Windows 8.1 you need to enter a password.
To save time and automatically open your session, you can disable this feature.
Deactivate Password at Login Screen in Windows 8.1
From the Home screen, tap Windows + R to launch the Run window.
Then, type control userpasswords2, and click OK.
Uncheck the box next Users must enter a user name and a password to use this computer. Click OK, and enter your password to save your changes:
Moving forward, your sessions will start automatically.