Here are the PDF instructions, posted for convienience.
It's a bit contradictory, do I start the vehicle and go to the Media screen and leave it running, plug in the USB and follow the prompts from there or do I turn it to run but not start and go to Media screen then once it begins update I start the engine? See bold below.
Step 11 Go to media screen
CAUTION! Make sure no other device is plugged into any of the USB ports while performing
this reprogram.
If other devices are connected to USB ports during
reprogramming,
it may cause failure of files to be loaded which may cause the
radio to need replacement.
12. Start the vehicle and put the correct USB flash drive into the USB port.
13. Press Update Now. The timer screen will be displayed for 2 minutes. After 2 minutes the radio
will reset and the update will start
NOTE: During the software update the backup camera, radio, SOS and several driving
assistance features will be unavailable.
NOTE: Once the update has started the vehicle can be started so the battery doesn’t run
low.