Once you have downloaded a subtitle from opensubtitles.org, put that subtitle in the same place as the movie. Start the movie, and in VLC, right-click the screen and choose Subtitles > Add Subtitle Track. That will open up a normal folder like windows does, and find the subtitle you downloaded from OpenSubtitles. The file will have an .srt extension. (rather than html, mp3, xls, etc)

Unrelated to the subtitles: Man, feels like my eyes are starting to get not-great again. Nothing like before, but things sure are being a bit more blurry.

Tip (nothing to do with my eyes. That story is done): If you give that srt file the same name as the movie name, the movie will automatically see them, and you don't have to manually "add" the subtitle.

Now the time consuming part:
Go to about halfway through the movie and see if the subtitles are matching up with the movie. Well, doesn't have to be "halfway" - and honestly I check multiple points in the movie to make sure - but you just want to be a bit in to make sure it's right. If the subtitle is out of sync from the audio, you have to shift the sub, at SubShifter. On that page, you see the "shift" area on the left side of the screen. You'll want to choose the subtitle file that you want to shift/correct.

And then the time-consuming part is choosing how much to shift the subtitle file. So, start playing the movie with the subtitles on, and manually calculate how far off the subs are. For example, maybe you will hear someone say a line in the movie, but the subtitle doesn't show that line for 3 seconds. Well, you want to shift the subtitle 3 seconds. Think about it in terms of the subtitle file.

• If you see the subtitles 4 seconds before the line is said in the movie, you want to shift it +4.0 seconds.
  
• If you hear the line in the movie 2 seconds before the subtitles pop up on screen, you want to shift it -2.0 seconds.
  

Then click resync. It will do all the work, and will download a new version of the subtitle, but it will say "resync" in the file name.

Repeat that process until you get it like you want it. Maybe you counted wrong and are still sone second off. Load up the new resync'ed file (Or just use the original again, but adjust the time) and try again.