Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Image
CK_DOODLE_PREVIEWParameter: >
CK_DOODLE_CHOOSEParameter: Link
CK_DOODLE_IMAGEParameter: Title
CK_DOODLE_TITLEParameter: Description
CK_DOODLE_BODY