How I can install Apple TV app on fire TV or LG tv?

If your Fire TV and LG TV devices are supported, you should be able to download the app from each device's App Store.

See here: Apple TV app - Devices - Apple

and here: Set up the Apple TV app on your smart TV or streaming device - Apple Support

https://www.amazon.co.uk/Apple-Inc-TV/dp/B07XDD7GYT/ref=sr_1_1?keywords=Apple+TV&qid=1584731221&s=mobile-apps&sr=1-1

https://gb.lgappstv.com/main/tvapp/detail?appId=990564&catCode1=&moreYn=N&cateYn=N&orderType=0&headerName=&appRankCode=&sellrUsrNo=

For help downloading it from each store on your device, please contact the Amazon, and LG support websites.

Those are links to the U.K stores. Note the address. amazon.co.uk and gb.lgappstv.com

Please study https://www.apple.com/apple-tv-plus/ and also https://www.apple.com/apple-tv-app/

NOTE: Apple TV app and Apple TV + are two totally different things. Study to learn the difference!!!!!!!