First - read the manual so you have some idea of what your about to do an where you need to go in the bios to make the changes you'll need to do as well as the raid utility.
Second - download your raid drivers for when you go to install windows. What they need to be on (floppy disk or flash drive, cd...) depends on which version of windows you plan on installing.
Install drives with power off.
Power on and Go into bios and change sata (or ahci) to raid mode. save and reboot.
Press ? ctrl F (if i remember right) to enter the raid utility when prompted on your screen.
Configure the raid.
Initialize the raid.
Save and reboot.
Install OS. (have raid driver handy)