Unfortunately, experts at eNotes are not in a position to do student assignments in lieu of the student. There is only one method for transcribing an audio file that will fulfill the course assignment requirements and that is to listen and recall and write what you hear.
Play a short bit of the file. A comfortable sized "bit" for a non-native speaker may be 3 to 5 words or a recognizable phrase. Pause the audio. Write down what you heard, or believe you heard. Play the next bit. Pause. Write what you heard or believe you heard.
Continue until you have worked through it once. Read what you have written. Start again at the beginning with play, listen, pause, write, play, listen, pause, write etc. You will recognize words you misheard or misrecollected. At each of these, pause the audio and make the correction.
For instance, the second sentence is "Somehow I ended up on a flight to LA instead." After first hearing it, I wrote it this way: "Somehow I wound up on a flight to LA instead." When I listened a second time, I recognized that I recollected incorrectly and changed "wound" to "ended."
My natural instinct was to wonder if this could be done automatically by a computer. If the following post (now two years old) is any indication, we are not there yet:
However, you may want to look around on Google for "transcibing an audio file" and see if anything more effective has developed in the past two years.
Almost forgot. I'm not a native. That's why I needed a help.
It's funny and strange. My question was not "HOW to", but ti was "Please".
I'd asked " Please do transcribe this audio file for me".