I've never used bitornado, but I'll assume it is about the same as Azureus..
So you download the .torrent file from suprnova, save it to your desktop.. then open bitornado and open the .torrent file with bitornado.... this should start your downloading.
One thing I will mention, seemed like the first few times I tried, I had some connection issues, but as I went along, they went away.. not sure if it is a recognizing the network thing, or just my imagination... but just FYI...
Let me know if you have done this, and if so if it doesn't help.