Without the .png file you can't get navigation.
Can you not just drag it over to the USB from where you downloaded it to? i.e. from where it is on the downloaded location to the USB - D:, E: or wherever your USB is on the computer. You don't try to open it just drag it over onto the USB and put it in your car's usb port. Then go to settings- display- edit wallpaper and touch the screen which should activate it and it should ask you to install the navigation sd card top right. Once the card is installed navigation should show up. If it doesn't, do a reset.