add audio source component to player prefab then in the Game Editor panel of adventure creator click sound (located under scene prefabs, logic in the game editor scene tab)
drag it into your player prefab click on your player prefab drag the sound prefab to the sound child field (located under player script component, audio clips in the inspector view of your player prefab)
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i copied the Brian2D prefab to do this,
add audio source component to player prefab
then in the Game Editor panel of adventure creator click sound
(located under scene prefabs, logic in the game editor scene tab)
drag it into your player prefab
click on your player prefab
drag the sound prefab to the sound child field
(located under player script component, audio clips in the inspector view of your player prefab)
then just add walk sound