If you would like to dictate documents or transcribe audio files in O365, here are instructions on how to do that.

Dictate:

• Open O365 Word online (this does NOT work in the desktop app right now)
• Open a new Word document
• Under the Home tab click Dictate
  • 
  • A microphone will pop up and glow blue when it is dictating
  • You will see your text appear in the document

Transcribe:

• Open O365 Word online (this does NOT work in the desktop app right now)
• Open a new Word document
• Under the Home tab click the small down arrow next to Dictate
  • 
• Click Transcribe
  • 
• Here is where you can upload an audio file or start recording a new file
  • If uploading, it'll transcribe your audio file and upload a copy to your OneDrive
  • It'll also break the recording out by speaker
  • You can edit your transcription as well if you notice the transcription picked up a wrong word.
  • Then click Add all to document and it'll add the Audio file with the transcription beneath it

If you choose to Record a new file, you're using Word Online as the audio recorder, and you can still type in your document.  For example, if you're in a lecture and want to record the presenter, it will record them while you continue working in your current document.

I'm attaching this YouTube video as a walkthrough for further information.