www.naviextras.com
you will need to sign up to this site , pick your car, then download the tool box, get a usb stick , say a 16gb one , format in pc at fat32 (from memory) remove all sticks from car and put this one into slot 1 , on car radio settings , then system (from memory) there will be one saying update sat nav or similar, this will make a file on the stick , remove once complete , go back to laptop insert load the toolbox and proceed from there, once its down loaded and copied to usb , go back to car , same menu as above (update nav) and it wil search and update which can take ages
one piece advise i would give is make sure the car is in run as if like the hs it turns the radio off after so long as if its updating during this time will cause issue if that make sense
all above from memory so if you get stuck give me a shout