Follow the given steps to active disneyplus on your amazon firestick tv.
Turn on the amazon firestick tv and go to the Apps area
Search and install the Disney Plus app on your device.
Open the app, then sign in using your existing login information. You'll get a special 8-digit code.
Open your web browser to access the Disneyplus.com login/begin URL and fill the 8-digit number code that you pop up on screen.
Click the "Continue" button to complete the activation process.