Jim,
Go to the full shopbot web page and from there you can download the latest control software. It will be 3.something and load it onto the computer that you are going to use with the handibot.
Also get the phone number from the same place and ring them up. There will be a small transfer fee ($50?) but that will get you a code for downloading and activating Vcarve. If the first owner never updated his/her license then there will be another charge to upgrade to the latest version. I highly recommend this as Vcarve has come a long way in the last two years.
Staff has talked about both a full trade in program as well as a fabmo card in the works but I have not seen an update in a while.
Your handibot is fully compatible with Fusion right now, just a matter of figuring it out. I keep hoping they (handibot guys) will put out a quick start on this. I do a lot of my design work in fusion but I have yet to figure out tool paths in it yet.
Vcarve is the place to start, when you get good there you can start experimenting in other things.
Another free piece of SW to consider is Sketchup, the latest versions of Vcarve will import Sketchup directly and very nicely.