The subtitles are in the „c3subtitles“ subfolder on mirror.selfnet.de available for download.
If you can't find a file with the same name than the video this means that there are no subtitles available.
If you want to use the *.srt-file just put it next to the video-file or like on mirror.selfnet.de in a subfolder „subtitles“. Common video players like VLC will find the file automatically.