Analytics Builder is part of the Streaming Analytics application in Cumulocity IoT. You start the Streaming Analytics application using the application switcher which is available in the top bar of the Cumulocity IoT user interface.

For detailed information on how to use Cumulocity IoT, see https://www.cumulocity.com/guides/.

Ask your administrator for the URL that is required to start Cumulocity IoT.