Follow this step by step guide:
- From the Main Menu scroll to hover over Settings.
- Click on My Fire TV.
- Choose Developer Options.
- Click Apps from Unknown Sources.
- Choose Turn On.
- Return to the Home Screen and click on the search icon and then type “Downloader” in the search box.
- Select the Downloader app and install it.
- Click Open.
- Select Allow if presented with this prompt.
- Click OK.