Simply add an "Integrator" Advanced Shape from the "Advanced Shapes" pallet of the "Flow Shapes" pull down or pop-up menu while editing the Flow Rule in the Flow Rule Form. You can then connect the integrator shape to the flow at the point you want to invoke the Connector Rule. To actually invoke the Connector Rule you will need to call an Activity Rule from the Integrator Shape. You can create the required Activity Rule by using one of the Pega Designer Studio Connector Wizards (DesignerStudio>Integration>Connectors>...). Please consult with a Senior System Architect on you project to help you create the requisite Connector Rule and associated Activity Rule.