APK files are no longer needed once you have installed the app, so by downloading ES File Explorer, you can locate and delete all of the APK files stored on your device to free up more storage space.
From the home screen on your device, select the lens /search icon icon in the top-left corner
– Type the name of the app ES File Explorer
– ES File Explorer will appear in the search results when you have typed the first few letters
– Click ES File Explorer icon on the next window
– Click Get or Download (depending upon what you see)
– Wait while the app is installed
– Click Open to run the app
Once the app is open, click Local > Home (2nd one) in the left menu OR click where it says Internal Storage on the top
3- FireStick folders appear on the right. Open the folder in which the files you need to delete are stored. The main folders will likely be DCIM, Download, Downloader, Movies, Music, and Pictures.
4- Select the file you wish to delete (say an APK file)
Note: DO NOT click the selected file
5- Now, hold down the Select button on your FireStick remote (the circular button) until the checkmark appears on the bottom-right of the file
6- Navigate to the bottom menu of ES File Explorer and click Delete
7- Uncheck Move to recycle bin
This is how you delete the files on FireStick with ES File explorer, repeat this process for all of the APK files on your device.