When you're watching a channel, Push touchfield on remote, then Channel information shows up, then swipe to icon left to the "movie reel" icon. If they're available, then you can activate them. And if available, choose between different lanquages.
Note: Some channels use teletext subtitles, and they dont work with KODI and IPTV SImple PVR. Note 2: Some Scandinavian channels use hardcoded subtitles. They can't be changed or removed.