Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Radius
ARRAYOBJECT_RADIUSParameter: Copies
ARRAYOBJECT_COPIESParameter: Amplitude
ARRAYOBJECT_AMPLITUDEParameter: Frequency
ARRAYOBJECT_FREQUENCYParameter: Array Frequency
ARRAYOBJECT_CIRCLEFREQParameter: Render Instance
ARRAYOBJECT_RENDERINSTANCES