Amazon Smart Thermostat doesn't have a speaker or microphone. For voice control, use a compatible Alexa-enabled device, like an Echo (sold separately), or the Alexa app.
Before purchasing, use the link “check compatibility” to see if the thermostat will work in your home and to determine if your home needs a C-wire power adapter.
Amazon Smart Thermostat requires a C-wire or a power adapter kit. Use the compatibility checker to see if your home has one already. Guided installation instructions are included in the Alexa app.