The Sothink Movie DVD Maker software supports SUB, SRT, TXT, and SSA subtitle formats and it doesn't have an option/tool on its interface to add a subtitle. However, if you name the subtitle file as the video/movie and you place it in the same directory, the Sothink Movie DVD Maker will bundle it with the output file. All you need to do is to make sure that it shares the same folder and it has the same name as your video/movie file. If you have problems, I recommend you contact the developers.
