Basically all you're doing is switching from your Windows operating system to your Mac operating system. So all you need to do is restart the computer by shutting it down and restarting. Navigate to the start button, and then select restart from the shutdown menu on your taskbar. When the computer begins to restart you're going to hear a bong sound when you hear that bong sound you need to hold down the option key on the keyboard once this is done you will see on the screen after a few minutes other operating systems select the Mac operating system. You can select it with the keyboard or you can simply use the mouse to click on the operating system that you want. Your computer will then launch into your Mac operating system and then you simply need to select the user you would like to log in as.