1. From the Device’s Main Menu scroll to hover over Settings

settings

2. Click My Fire TV

Click My Fire TV

3. Choose Developer Options

choose developer options

4. Click Apps from Unknown Sources

click apps from unknown sources

5. Choose Turn On

NOTE: Turning on Unknown Sources is not needed to install Downloader. However, to install any 3rd party applications via Downloader, this must be enabled.

choose turn on

6. Return to the home screen and hover over the Search icon

search icon

7. Type in Downloader

type downloader

8. Select the Downloader app

select downloader

9. Click Download

click download

10. Click Open

click open

11. Click Allow

click allow

12. Click OK

click ok

That’s it!

To use all features of this app, I also suggest Enabling Javascript within the Settings of the application:
Turn on Javascript

You can now use Downloader to Install apps and APKS with ease.