Yeah, need a comprehensive install guide. I think they're working on it.
I had the same problems, so here's what I did...
First - did the driver install properly? No errors? That's got to be first.
Then, grab that DigiXAddons zip file and unzip it into a temp folder, don't try and unzip it in-place.
From where you unzipped it, copy the "hardware" folder, then paste it into your "My Documents\Arduino" folder
You'll then have something like "My Documents\Arduino\hardware\arduino\sam\<stuff>"
Restart Arduino IDE
Does that work for you>