It's pretty easy to add subtitles to a movie already playing in the VLC Media Player. Go to File > Open and locate a movie file. Play the file, then simply locate or download a subtitle for the movie you're playing and use Subtitle > Add Subtitle file from the menu bar, or simply drag and drop it in the playing window. To configure Subtitles, go to Tools > Preferences > Subtitles OSD. You can change various aspects of the subtitles loaded in the player.