You need to set up your Fire TV Cube when you first get it, or after resetting it. You can also set up a Fire TV Cube to control your TV and other devices.
Second Gen Fire TV Cube Review: 'Alexa, control my TV' - MobileSyrup
Fire TV Cube Review: Alexa Gets Overwhelmed - CNET
Fire TV Cube (3rd Generation) Review
announces third generation Fire TV Cube and new Alexa Voice Remote Pro - news
Fire TV Cube review: great smart TV box, irritating smart speaker
Fire TV Cube - 5 Reasons Why You Might Want To Upgrade NOW! — WhatGear, Tech Reviews
Fire TV Cube on the way (maybe with a mic, speaker, and Alexa support) - Liliputing
Fire TV Cube Review: Great benefits for voice-control with streaming services yet a work-in-progress on full connectivity – Critical popcorn
Fire TV Cube Review: Perfect for the right home
How to set up an Fire TV Cube
Fire TV Cube (3rd Generation): a beefed up smart streamer with Alexa at its core
Overview of the Fire TV Cube's Equipment Control Setup Process