Redirect URIs do not match - WebRTC JS Demo

I'm a new developer, so please bear with me, but I'm trying to spin up the demo and I get an error response the the Redirect URIs don't match. In the app settings I have a localhost redirect URI since I'm running the demo locally. I'm sure that this is a problem with my understanding of OAuth flow for this demo.My app is a Browser Based app, and Im working from this repo https://github.com/anilkumarbp/ringcentral-web-phone/tree/feature/OAuth-2.0/demo for the demo. I have the VoiP enabled for my app. If it is simple enough to explain or redirect me to an explanation I would appreciate it.