Hi Danielle, I'm sorry I can't be of much help on this one as I don't officially offer transcription and only do so very rarely for select clients.
I'd suggest that if you're 'not sure how it works' you may wish to pursue a lesson in the process before offering it. (Just my 2 cents

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When I do need to perform this task though, I just use my standard MP3 player like Winamp or Windows (I've only ever received digital files for transcription) OR I also like Audacity which is a sound file editing software but also works great for this - particularly when the original file needs to be edited and accompany the transcription on return to the client.