The built-in App store on the Kindle Fire offers a decent selection, but it doesn’t have everything. For example, you can’t download Tweetdeck or TripIt, or alternate browsers like Opera Mini or Firefox. While Google’s Android Market is off limits to Kindle Fire owners, you can install apps that aren’t available on Amazon’s store by transferring them via USB (also known as sideloading).
Here’s how to sideload apps on the Kindle Fire.
In order to sideload any app, you’ll need to get a copy of its APK file and save it to your PC for transfer to the Kindle Fire. You can download APKs directly from handango.com, a store that has a really strong selection and makes its wares available via any web browser.
If you have another Android device that has access to the Android market, you can use Astro File Manager, another free app, to create APK backups of any app you have installed. Then you can copy them from your device to your PC for transfer to the Fire.