Charts require some type of count, whether it’s a standard measure, or one that’s been created using the Variable Editor on the Edit Report page.
Once the report generates, highlight the table and select Turn Into.
The Report Element panel to the right will open to show different types of charts (and tables) to choose from:
Another option to create a chart is to insert one without data. Under the Insert section of the toolbar, select "Insert Chart", and then click into the report where you would like the chart to go.
Once a chart is created, Data assignment is done through the feeding panel:
And other edits can be made through the Report Element Format panel options like the Title, the legends, the color palette, and the data types.