I too got this update message . I assumed it meant the car had already downloaded the update and all I needed do was install it. But when I pressed the button nothing much happened.
The reason was although my car is connected to my home wifi network, my driveway is out of range . But by moving the car to the side of the house it does get a signal to my wifi and then pressing the button started the process. It connected to my wifi and then displayed a downloading-in- progress bar, which takes a few minutes. On completion you can install it. This does cause the car screens to go blank for a short time, which was a bit disconcerting but presumably just rebooting.
I think you will need to find a way of connecting your car to a wifi network. Maybe via your phone, but sorry I cant help with that
My new found experience means I could possibly do HERE map updates via wifi, but I will probably contiue to do so via usb stick.
