If you have NAV it's easy...just download the file and extract the contents to a blank formatted FAT-32 USB drive and insert it into your truck with key on, engine off with a battery charger hooked up or turn truck on and allow it to idle. After it's inserted you'll see on the touchscreen about 5-10 mins later "updating system software" and it'll then take 25-45 mins to finish.
If you don't have NAV the process is more complicated because it entails breaking up the install into two parts because the APIM doesn't have enough memory to do it in one shot. ** you would think the NAV version would be bigger but it's not, the non-NAV one is bigger **