For a high-definition BluRay rip (like the 1080p version), you typically need an .SRT or .ASS file.
Some older subtitles only translate dialogue, leaving signs or letters untranslated. The Blu-ray.com review notes that the official English subtitles are well-done and cover the essential context. subtitle The.Angry.Guest.1972.1080p.BluRay
Rename the subtitle file to match the video file exactly (e.g., The.Angry.Guest.1972.1080p.BluRay.srt ). For a high-definition BluRay rip (like the 1080p