Modifying a visualization
When a new visualization is created, a suggestion of what to visualize is created by default. You can then modify the visualization to show the values you are interested in by changing the columns shown on various axes, changing the aggregation, the coloring, etc.
Columns and aggregations are changed using the column selectors directly in the visualization, whereas appearance settings are specified using the visualization properties. Right-click the visualization, and select Properties in the opened menu, to change properties.