To see [insert your language here] subtitles on a YouTube video:
1. Click on the "Subtitles" icon that is at the bottom of the vid to turn subtitles on.
2. Click on the "Tools" icon, then select *Subtitles* from the menu to choose your language.
Here's Google's explanation, if you want more details. You can also use Google Translate (steps are in the link) if the vid does not already have subtitles, but it doesn't always work. I couldn't listen to a Russian one the other day. Hope that's helpful.