At the bottom of the audio list, tap "Add audio track" or "Open audio file" (depending on your version).
If you have a different version of the same movie in Hindi, you can use tools like VLC Media Player or Handbrake to extract the audio track into a standalone file. How To Download Hindi Audio Track In Mx Player
Only download audio tracks for movies you own. Piracy is illegal and harms the film industry. At the bottom of the audio list, tap
Would you like step-by-step commands for muxing with MKVToolNix or a mobile app recommendation? How To Download Hindi Audio Track In Mx Player