Narration is the Sound of Structure
Do NOT use Narration to do staging. In Audio-Movies, we always avoid the tendency to use too much exposition. Yawn. Let the sound setting, as well as activities, communicate the visual to the mind.
Never include simple stage directions being told by the Narrator. That's looked after by stage-direction.
In SOUND we thrive on the echo of movement, and the sounds of the setting that creates an image in the mind.
Sounds of Narration
"Days Of Heaven" has some very effective Narration for Film. Have a look at it. Then go back to the start - play it again and listen with eyes closed... Just click the link.
https://www.youtube.com/watch?v=EzZ8phk8yYc
If you play the "Stand By Me" trailer, it will give a great sense of the film. And let you hear the opening Narration, which would also work in Audio Only format...