Consult your motherboard manual, but overall it should be pretty easy to do RAID0 with those. You'll need to install your OS from scratch. I'm assuming you're using Windows, since the "software with hardware assist RAID" those boards support is Windows-only.
Basically, you'll need to attach the two drives to the board, then run the RAID BIOS software as your machine boots. During POST it will tell you the hotkey to push. You may have to enable RAID in the BIOS, I cannot say for sure because I've never used a P5N.
Once you're in there, it's a simple matter to create an array. RAID0 is what you want, and from there you'll need to reinstall Windows. The motherboard should have come with a driver disk you need to give Windows during the install (it'll actually prompt you to push a button once the install CD begins loading, which you will need to do). Once you've loaded the driver, the install proceeds as normal.
With RAID0, you must understand that if one drive dies, you lose 100% of your data. Make sure if you keep anything important on this array that you backup the data to another place routinely.
If you DON'T want to install your OS to the RAID0, and merely add a RAID0 to your existing install to, say, install games on or use for video or audio editing, it's even simpler - you can add the drives and create the array, and assuming Windows is still booting at that point, load the driver into Windows post-install, then format the new array.