Just to add to my earlier note, I have reviewed my records. The part No. XS90199 is indeed the Rand McNally dongle. It has to be plugged into USB 1 at the back of the head unit (not the input on the front). However, Thor have extended that input to the top of the dash so you could put it in there. I chose to fit a USB splitter behind the unit to hide the dongle away.
Two things: 1) you will need a wifi hotspot on board to provide the necessary internet connection. 2) to activate the feature, with the navi. screen showing, remove and replace the SD card in the head unit to reboot the nav system. That card carries the RM mapping data etc
Edit: I should mention that the maps have a free lifetime update and I don't recall the literature provided saying anything about that. My earlier experience was with the RM stand alone navigator.
Go to the RM website on your computer with an SD card slot and search for the Rand McNally Dock software download. Once installed, you should then insert the SD card from your radio to register your device and get updates if any are available.
Hope all this helps.