Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Strength
MGPUSHAPARTEFFECTOR_STRENGTH
Parameter: Selection
MGPUSHAPARTEFFECTOR_SELECTION
Parameter: Mode
MGPUSHAPARTEFFECTOR_MODE
Parameter: Radius
MGPUSHAPARTEFFECTOR_RADIUS
Parameter: Iterations
MGPUSHAPARTEFFECTOR_ITERATIONS