Stephen Bennett has two videos lessons from Truefire for Harp Guitar. Both are excellent and will get you up and going. There are several ways to tune the sub bass strings. I recommend Gregg Miner's website for tons of information about harp guitar and he is a great resource for strings.
http://harpguitarmusic.com/
If you are close to North Carolina come to the Harp Guitar Gathering, Oct 18-20 in Mooresville NC.