From the FAQ in the App;

Please use your google assistant app to find "Netro Sprite", either by directly typing "talk to Netro Sprite" or searching through the google assistant explorer. Then tap the "link" button, and you will be redirected to the account login page. After using your Netro account to be successfully linked, you will be able to use google home to work with Netro. You can talk to your Google home like: "Hey google, ask Netro Sprite to water zone two for 5 minutes." or "Hey google, ask Netro Sprite to stop watering." The Netro Sprite should start/stop watering accordingly.