Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Radius
ARRAYOBJECT_RADIUS
Parameter: Copies
ARRAYOBJECT_COPIES
Parameter: Amplitude
ARRAYOBJECT_AMPLITUDE
Parameter: Frequency
ARRAYOBJECT_FREQUENCY
Parameter: Array Frequency
ARRAYOBJECT_CIRCLEFREQ
Parameter: Render Instance
ARRAYOBJECT_RENDERINSTANCES