Data
Without data mapped to it the visual looks like this:
At least a measure has to be assigned to the "Measure" field on the "Build visual" space. The measure will show as a single chart and the formatting area will be populated with the visuals formatting options (see Formatting).
All data fields explained:
Measure - Value to be shown as a number of symbols on the chart. Must be numeric.
Legend - Grouping to be used to show symbols in different colors. Type numeric or text.
Multiples - Multiple to create a number of seperate charts. Type text or image (URI)