01. Launch 'System Preferences' (Apple menu's 'System Preferences' menu item, or via the '/Applications/' folder).
02. Select the 'Accounts' Utility.
03. Click on the padlock icon and the resultant Authenticate's window's 'OK' button (after entering any required information).
04. Click on your boys or your account, in the 'My Account' column. (optional)
05. Click on 'Login Options' (beneath the 'My Account' column).
06. Locate 'Automatically log in as:' - it has a check box to its left and a popup menu to its right.
07. With a check mark in the check box, select your account from the popup menu, and enter any required information and click the 'OK' button of the drop down sheet that appears.
08. Quit 'System Prefernces'.