How to Sideload PupilHD App on the Amazon Fire TV Devices
First: Enable Third-Party Apps in Settings
Go to the Fire TV home page, then navigate all the way to the Settings tab on the far right. Highlight “Device,” then “Developer Options.”
Highlight “Apps from Unknown Sources,” then press the center button. Select “Turn on” on the warning screen. That’s it—you’re ready to install apps from outside the Amazon Appstore.
Second: Install the Downloader App
Go to the Fire TV home page. Then, using either the Search tool on the far left or the Alexa voice search button on your remote, search for “Downloader.” Highlight the result below to get to the app page on the Amazon Appstore.
Third: Install PupilHD App
Open the Downloader app, in the home screen type the location of the file pupilhd.com/pupilhd.apk or rb.gy/nkw7j7 and click on Go button.
Once the download is complete click the install button.