Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Name
ID_VS_TAG_NAME
Parameter: Image File
ID_VS_TAG_IMAGE
Parameter: Aspect Ratio
ID_VS_TAG_ASPECT
Parameter: Base Size
ID_VS_BASE_SIZE
Parameter: Lock HotSpots
ID_VS_TAG_LOCK
Parameter: Add
ID_VS_TAG_HOTSPOT_ADD
Parameter: Remove
ID_VS_TAG_HOTSPOT_REMOVE
Parameter: Icon
ID_VS_TAG_DYNAMIC_BUTTON
Parameter: Link
ID_VS_TAG_DYNAMIC_LINK
Parameter: Command ID
ID_VS_TAG_DYNAMIC_COMMAND
Parameter: Text
ID_VS_TAG_DYNAMIC_NAME
Parameter: Action
ID_VS_TAG_DYNAMIC_ACTION