Thank you for reaching out to us using our online Answers Forum. I can understand you want to use the audio only feature available with our applications. I would be glad to help you get that set up. All you do is tap the screen of your mobile device. Then you tap "Quality". Then you just select "Audio Only" that will set it to the audio only mode.
Here is an article explaining how to do it:
Hope this helps!
The Sling Media Moderation Team