No you have Airnav installed, download the drivers from the link. They are in a zipped file so unzip to a location you can find, I would suggest you make a folder on your desktop and name if 8 Drivers.
I dont have Windows 8 but here are the instructions for Windows 7. Click on devices and printers and you should see your Radarbox on the bottom row. Right click on it and click on Properties. Click on the Hardware tab and then Properties then Change Settings, then Driver, then Update Driver, then Browse my computer for driver software then direct it to where you put the unzipped drivers and finally next and the drivers should be installed thereafter.
Alan