Adding subtitles to NTSC DVD

I am looking for working guide on how to add new subtitles and re-author a NTSC DVD. None of the guides I have found so far seem to work. Anyone can help?

First, demux all Video & Audio streams of the DVD main movie with VobEdit. Load these into DVDLab Pro. Load the video & audio streams in, then your Subtitle stream (you may have to convert your sub stream to simething it can accept, *.srt streams work well), compile, test and burn.