The brand alone is not enough
Check the TV operating system and model year. LG webOS, Samsung Tizen and Android TV have different stores and apps. Fire OS Downloader instructions do not apply to every Smart TV.
Choose a guide by system
Choose the compatible checkout app for LG and Samsung. Follow the Anume Player guide for Android TV / Google TV. If you use a Firestick through HDMI, follow the Firestick guide regardless of the screen brand.
Before activation
Install the app, check its identifier and request a trial through the official form. A trial lets you check your device and network before choosing a subscription. Do not assume a player includes a TV service.