To embed an external mp3 audio file in an Edublogs post, follow 7 steps: 1) select the Embed Flash button and enter the mp3 player URL and dimensions, 2) add the player code to the post, 3) enter the mp3 file URL in the correct format within the player code, 4) select the visual button, 5) save the post, and 6) preview to see the embedded mp3 player displaying the audio file.