Download a new paid app for free every day on your Kindle. open the Appstore to find the free app of the day at the top of the screen. Press the orange "Free" button and then confirm your order by pressing the green “Get App” button.
You can also find additional Appstore deals on your computer. Go to www.amazon.com/appstore, and click "Deals" in the navigation bar below the search box to see all current Appstore deals.