Ars Technica has a good overview on getting the consumer preview of Windows 8 up and rolling.
The Windows 8 Consumer Preview drops you in at the deep end. Unlike Windows of old, which has taught users how to handle the user interface with mouse tutorials and bouncing arrows, Windows 8 just dumps you at the lock screen. Swipe or drag that out the way, and you’re faced with the brand new Start screen. This will be a bit of a shock to existing Windows users (which is to say, virtually every person on earth who has ever owned a computer), and getting to grips with the Windows 8 interface is going to require some effort.