1) Download the free demo version of the Capture software from here
Capture Download Page
2) Download the attached Capture show file and then unzip it.
Install the Capture software, open the demo show file and it should all work. The only limitation is that the demo version of the Capture software will shut down every 90 minutes, but it only takes a few seconds to get it going again.
In order to get Capture to talk to Clarity you MUST have an active network connection. If your Mac is not connected to a network then simply go into the Airport app and select "Create Network", this allows you to create a simple computer to computer stand alone network. There is no need to actually connect to anything, you just to create it - to trick the Mac into actioning the Art-Net data.