Make sure you have Lingq extension added to Chrome browser (not sure if there is a firefox version or not). Start watching a movie/tv show on Netflix...make sure the subtititles you want are selected. Click the Lingq import button (browser extension). It should import the subtitiles into a lesson.
I have not used this a lot myself. I'm still not at a level where I can understand much as I'm watching, even with subtitles on. I have watched an episode of a tv show and went through parts of it in Lingq. I've watched a movie and went through most of it in Lingq afterwards.
Some issues I've found...it can be hard to know who is talking, or when it changes speaker. Mostly you can derive this from context, but if there are several people in a scene, you may not know who is speaking in the subtitiles when you look at it in Lingq later. Unless the subtitles have the name of the character. In one show I was watching, the scene had two characters, plus the tv playing that they were watching and the subtitles were there for what was being said on the tv show they were watching. That makes it confusing when you come back and read the subtitles in Lingq...you basically end up with two conversations intermixed =D. Totally understandble when watching, but confusing when reading alone in Lingq.
Another issue, at least with the German language movies/tv shows, is that the subtitles often don't match the actual dialogue. i.e. they'll use simple past tense in the subtitles, but the dialogue is in present perfect. Or they'll make other changes, probably to "tighten" things up for reading quickly.
I think I'll use the feature more as I get stronger. Much of the vocabulary in movies is a little out of my range so it can be a little tedious to walk through. Plus there is so much to go through. I prefer much shorter stories, dialogue, that I can read in a few minutes.