In order to view USTVnow on your Kindle device make sure you are already a subscriber.
Open the Kindle browser
Go to the mobile page http://www.ustvnow.com/mobile
Tap on "Login"
Type in your USTVnow user-name and password and tap on "sign in"
You can always open a ticket if you need further assistance.
Note: USTVnow mobile website is compatible with Kindle Fire HD.