Hi there. You missed an important file on the downloads page.
Go back to the page you downloaded the file. Look slightly above the link like 1 centimeter, there is anoter link for the firmware updater software. You need both things:
-The firmware file you downloaded.
-The firmware updater software (that you didn't download and install yet)
Once you install the firmware updater software and open it, there are numbered step-by-step instructions on how to do the upgrade.