The BACnet mapping configuration and setup menu is normally located under the main menu bar. If the BACnet menu item is not available, make sure you are logged in with at least Configuration or Administrative privileges to Fresco.
The BACnet menu is also only available on the Fresco Master controllers. The Fresco Master controller is the Fresco with a Controller Id of 1. Each Fresco on the Fresco system can have a different Network Id, but the BACnet menu is only displayed and configured on the Fresco units with Controller Id of 1 (the Fresco Master).