How do I add Subtitles with Nero 9?

I have searched the forum and couldn’t find anything that had a reply when the topic was subtitles… Maybe I didn’t do it correctly, but in any case…
How do I add subtitles to Nero 9? I have downloaded a Thai Movie called “Tsunami” which is in Thai language with subtitles in English.

The two files are in a folder called subs and are an “.idx” file and a “.sub” file.

Thanks in advance for any help.

Not familiar with 9, but 6 and 7 have no sub support in Nero Vision.