Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Shape
FP_STANDARDEMITTER_SOURCE_SHAPEParameter: Size
FP_STANDARDEMITTER_SOURCE_SHAPE_SIZEParameter: Born
FP_STANDARDEMITTER_OUTPUT_BORNParameter: FP_STANDARDEMITTER_OUTPUT_BORN_ATTRIBUTE_NAME
FP_STANDARDEMITTER_OUTPUT_BORN_ATTRIBUTE_NAMEParameter: Create
FP_STANDARDEMITTER_OUTPUT_BORN_ATTRIBUTE_CREATEParameter: UVW Coordinates
FP_STANDARDEMITTER_OUTPUT_UVWParameter: FP_STANDARDEMITTER_OUTPUT_UVW_ATTRIBUTE_NAME
FP_STANDARDEMITTER_OUTPUT_UVW_ATTRIBUTE_NAMEParameter: Create
FP_STANDARDEMITTER_OUTPUT_UVW_ATTRIBUTE_CREATE