I downloaded a movie called The.Nude.Vampire.1970.720p.BluRay.x264-x0r.mkv.mp4, but it's a French movie with no English subtitles. When you want the subtitles they are not there. :-)
Subtitles are sometimes embedded in a movie and sometimes they are independent files outside of the movie. You can search on line for theses subtitle files, I found one for this movie at isubtitles.in
It was a zip file. I scanned with my anti-virus first, Avast, and the with SuperAntiSpyware. You can use whatever security programs you have on your system by just right-clicking on the file and looking for any option to scan with...
This file got a clean report so I uncompressed it and there was two files inside a read me text file which only had the website address typed in it and a file called The Nude Vampire (La vampire nue) 1970.srt.
Usually you just place this file into the same folder as the movie but it didn't work. Since I use VLC it was just a matter of clicking on the word Subtitle, top menu, and then Add Subtitle File... Find the file just downloaded and click Open.
There is a little trick where you can get the subtitles start up automatically with the movie and that is simply to rename the subtitle file to match the movie or rename the movie to match the subtitle file.
I decided to rename the movie to
The Nude Vampire (La vampire nue) 1970.mp4
The subtitle file,
The Nude Vampire (La vampire nue) 1970.
Simple as that.