Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Simulation
PBD_LIQUID_SIMULATION_PRIORITYParameter: Enable
PBD_LIQUID_USEParameter: Mass
PBD_LIQUID_MASSParameter: Radius
PBD_LIQUID_RADIUSParameter: Friction
PBD_LIQUID_FRICTIONParameter: Bounciness
PBD_LIQUID_BOUNCINESSParameter: Stickiness
PBD_LIQUID_STICKINESS