Rename the subtitle file to match the movie file exactly. Example: Piranha.3DD.2012.mp4 and Piranha.3DD.2012.srt .
Look for a file that matches your specific movie version (e.g., "BluRay-720p" or "BRRip"). Piranha 3DD subtitles Estonian
Often the most reliable source for international subtitles. Search for "Piranha 3DD" and filter by Estonian. Rename the subtitle file to match the movie file exactly