Here are the instructions for renaming your new Kindle Fire Device:

1. Login to your Amazon.com account
2. Scroll to bottom and click “Manage Your Kindle”
3. On left side under “Your Kindle Account” click “Manage Your Devices”
4. Find your Kindle, next to Kindle Name click “edit” button
5. Rename and click “Update”
6. On your kindle fire device, click settings at the top right next to wifi
7. Click “Sync”
8. Done