Where do I Find subtitles for les rois maudits?

You search for ".srt subtitles les rois maudits" in your google or Bing search engine.

".srt" refers to the subtitles file format, which is a small text file that you can open in Notepad or any text editor.

You rename the file so it has exactly the same name as your .avi/mp4/mkg/mpg video file, except for the .srt extension.

The other file format is .sub, which is what is used in the DVDs. But it's a graphic subtitles file format, which is very large and not supported by most players.

If you own the DVD, you can rip the subtitles yourself for personal usage, just like you can legally rip the video. I have no experience what ripper works best or which converts from .sub to .srt, as I usually rip the whole DVD without any down-conversion. There are also .sub to .srt converters (standalone software or online) if you have the .sub but can't find the .srt file. There are also sites to merge a 2-part set of .srt files into a single file, if your video file is a single file. Or the reverse, split one file in two.

Depending on where you live, the subtitles are probably protected by copyright, they may not be legal. Some specific movies, especially mangas, have their subtitles created by fans and placed in the public domain. Publishers have been known to use these subtitles when marketing DVDs to foreign markets.