You can use SW like
TitleDrome to add subtitles over the video image when playing the HD movie on a PC based environment. There are also some playback SW packages that support external subtitles (like Nero player). TitleDrome is not free SW but there's a Lite version that's free but comes with some annoying advertisement texts and the full version can be used for some time as a free trial as well before buying.
You need to find the subtitles from somewhere in the internet in
SubRip format. With Google searches it's quite easy to find sites that have loads of subs in SubRip format. I'm not sure about the legal aspects of internet distribution of ripped subtitles so I don't want to provide direct links for that reason.
I only tried it once with TitleDrome (on a free trial period) with another movie and it worked pretty well, however I don't really want to watch movies on my PC environment as I have to make do with a 24 inch display and stereo sound in that case.