Drag a system from the Drawings section on the right and drop it in the main section.
Drag a dataflow from the Drawings section on the right and drop it on the first item (system) that represents the flow you want to create. Then continue clicking on items to include in the dataflow.
You can also start a dataflow by right-clicking on an item and selecting New Dataflow…
When you’re done, right-click in a blank area and click Confirm Dataflow.