[Wlug] raid1

I'd like to set up Raid-1 on my computer. I have 2 500Gig hds, one of which is empty, and one of which has data (that I want to keep). I found this guide, https://wiki.ubuntu.com/Raid (I use Ubuntu), and liked the "super simple md" recipe, but I'm not sure how to do this so that I don't loose data. (I searched around, but the only thing I found required the alternate install CD, which I have issues with.) Any help would be appreciated. Simeon MacMillen