You can add a standard shape to a flow to emulate a task in a process. By using Process Modeler to integrate standard shapes with other shapes in your flow diagram, you can refine the sequence of events that a case follows at run time.
Note: Use Case Designer to add the Assignment shape or Subprocess shape to a flow. You can then use Process Modeler to configure the advanced options for these standard shapes.
Open a flow.
In the toolbar of Process Modeler, click the Shape palette icon 
to display a menu of shapes.
Click and drag a standard shape from the main menu to a position on the flow diagram.
Replace the default name of the shape with descriptive text that is fewer than 128 characters.
Double-click the shape.
Configure the shape by entering values in the property panel.
Click Save.
After the standard shape is connected to other shapes in the flow diagram, you can test the new functionality by running the flow.
Tip: To ignore validation errors while you work on a flow, enable draft mode.
For more information see: