The Google Home app is used to manage your smart Home device and set up new devices. You can download the Google Home app for free from the App Store or Google Play. Once you have downloaded the app, open it and follow the instructions to set up your device. You will be asked to sign in with your Google account and connect to your home's Wi-Fi network. After you have completed the setup process, you can use the Google Home app to control your device and add new features. You can also use the app to manage multiple devices if you have more than one smart devices in your home.