How start with windows 8 automatically using bootcamp?

When booted under MacOS, you can go to the System Preferences and select your "Startup Disk". This will allow you to indicate which partition you want your computer to boot from normally, or on just the reboot that you are initiating at that time. If you have already installed the Boot Camp Utilities under Windows, you can do similar from the tray icon that it loads. If you boot your Mac from teh Recovery Partition, one of the menu options is to specify the Starup Disk. You have many options to choose from.