Install Downloader

From the home screen choose Find and type downloader using the remote

Select downloader on the right

Select Downloader

Click the Get or Download button to download the app

Press the Home button on the remote to go back to the main screen

 

Enable Developer options

Select FireStick Settings

Click My Fire TV

Select About

 

Click on Fire TV Stick 4K quickly 7 times.  You will see a message on the bottom of the screen saying No need, you are already a developer

 

Press the back button once to go back to Settings > My Fire TV and click Developer Options

 

Click Install unknown apps and set Downloader to ON

Press the Home button on the remote to go back to the main screen

Install IMPlayer

Select Apps

Scroll down and choose Downloader

In the URL box enter 82375 then click Go

This should download the latest app. 

Once downloaded, click INSTALL to install the app.

Once installed, click OPEN

When prompted choose Allow

Read and click through the General Tips

At this point I will provide a Management Code

 

Accessing IMPlayer from recently used apps

After initially opening IMPlayer it will now show in recently used apps

Press the Home button on the remote to go back to the main screen

Press the down button 2 or 3 times to get to recently used apps

 

Optional: Add IMPlayer to top row for easy access

Select Apps

Scroll down until you select IMPlayer.  Then press the menu button on the remote

Choose Move to front

Press the Home button on the remote to go back to the main screen

You will now see IMPlayer on the top row