Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Strength
MELTOBJECT_STRENGTH
Parameter: Radius
MELTOBJECT_RADIUS
Parameter: Vertical Randomness
MELTOBJECT_VERTRANDOM
Parameter: Radial Randomness
MELTOBJECT_RADRANDOM
Parameter: Melted Size
MELTOBJECT_SIZE
Parameter: Noise Scale
MELTOBJECT_NOISESCALE