Because VAVOO is not available on the Google Play Store or Amazon Appstore, you must enable "Unknown Sources" before installing the APK.
On : Go to Settings > My Fire TV > Developer Options (tap "About" 7 times if hidden) and toggle Install unknown apps for the "Downloader" app. Download VAVOO apk
Open the downloaded file and follow the on-screen prompts. How to Use VAVOO Because VAVOO is not available on the Google