BET NOW and bet are not a subscription service. It's free to download the app, and you need to log in with your cable TV provider to watch locked content on the app or website. If you are looking to subscribe to a service, check out BET+ in the app store.
On Android and Kindle you can access the app on devices running Android 5.0 and above. To access BET+ App on Fire TV devices, you can sign into the BET+ app after it is downloaded to your device.