CNiGraph and all of the other CNi control classes derive from CWnd. You use the CWnd functions, such as CWnd::MoveWindow to move and size the controls.
There is an example program that ships with Measurement Studio for C++ that demonstrates this. It is available under the following path.
MeasurementStudio\VC\Examples\Ui\Common\Dynamic Move or Resize UI
David Rohacek
National Instruments