You can input your Amazon device activation code at Amazon.com/code, which is the official page used to register and connect Amazon devices to your Amazon account.
Here’s where and how to enter the code:
When you sign in on your Fire TV, Fire Stick, or Smart TV app, an activation code appears on the TV screen.
On any phone, tablet, or computer, open a web browser and go to www.amazon.com/code.
Sign in to your Amazon account.
Enter the activation code exactly as shown and select Submit.
After entering the code, your device will automatically register and be ready to use within seconds.