Using Below steps you can add dual audio to a Movie easily.
Steps to add dual audio to a Movie:
1.Download any of the movie (suppose English prints).
2.Download the other (suppose Hindi track) audio track
3.Download MKVToolnix form here:
4.Open Mkvmerge from the MKVToolnix startmenu entry.
5.In the Input tab,click "add" and select the movie you have just downloaded..
6.Again click "add" and now add the other audio file you have downloaded.
7.Click "Start Muxing" and in no time you will have your dual audio Movie.