For how to sideload on the Fire TV, see this guide from AFTVnews: https://www.aftvnews.com/sideload-apk-app-amazon-fire-tv-stick-cube-edition-firestick-downloader/
Use this code where you would put a URL: 391123
Delete the APK file from your computer and from the Android TV device:
If you want to keep X-plore File Manager and use it later, then you should still disable the “WiFi sharing option” by selecting it and turning it off: