Disclaimer: Ensure you watch movies through legal streaming platforms to support the creators. If you'd like, I can: Find where you can stream this movie legally

Ensure your downloaded movie file and the Sinhala .srt file have the exact same name (e.g., Sillunu_Oru_Kadhal.mp4 and Sillunu_Oru_Kadhal.srt ) in the same folder. Most media players will then load the subtitles automatically.