How to Put a Password on Your Computer When You Turn it On
Whether you use a PC or a Mac computer, a local account is used to store your data and secure your personal settings. Each local computer account must be configured with a unique password, but on most systems, the computer will automatically log in to a standard account during the start-up process. In order to better secure your computer and information, you can disable automatic login and put a password on your system for when the computer is turned on.
Open the Start menu and click on the "Run" icon.
Type "control userpasswords2" into the dialog box and hit "Enter." A window will open with various login information and settings.
Check the box next to "Users must enter a user name and password to use this computer."
Hit the "OK" button to save the settings.
Restart your computer. When the computer finishes booting up, you will be automatically taken to a login screen, where users will need to enter their password before accessing the system.
Click on the "System Preferences" icon in the Dock.
Go to the "Security" control panel in the "Personal" section.
Click on the lock symbol in the lower-left corner of the window and then enter your administrator username and password.
Check the box next to "Disable automatic login."
Close the System Preferences window and restart the computer. When the computer finishes booting up, you will be automatically taken to a login screen, where users will need to enter their password before accessing the system.