In order for the Timetable element to work properly, you first need to add columns in Timetable >Add Column panel on your dashboard.
Once you create columns, proceed to Timetable >Add Event panel, and add events. You can assign any number of columns to one event.
When both events and columns are created, go to page editor and select which of the columns and events will display in Bold Builder Timetable element.
For more information, you can read Timetable plugin documentation.