The FlowChart class is from an older version of the control and you shouldn't use it anymore. In version 5 its functionality has been divided between the Diagram and DiagramView classes. I guess you have flowchart.net.dll from an older installation - delete that file and remove the FlowChart from the toolbox. Add references to the following assemblies to your project:

mindfusion.common.dll
mindfusion.diagramming.dll
mindfusion.diagramming.winforms.dll

Now you should be able to drop Diagram and DiagramView instances in your form. If you have version 5.0.2, dropping a DiagramView will automatically create a Diagram object and associate it with the view.

I hope that helps,
Stoyan