Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Simulation
PBD_LIQUID_SIMULATION_PRIORITY
Parameter: Enable
PBD_LIQUID_USE
Parameter: Mass
PBD_LIQUID_MASS
Parameter: Radius
PBD_LIQUID_RADIUS
Parameter: Friction
PBD_LIQUID_FRICTION
Parameter: Bounciness
PBD_LIQUID_BOUNCINESS
Parameter: Stickiness
PBD_LIQUID_STICKINESS