Update README.md

Author: cloudwebrtc

README.md

@@ -1,9 +1,12 @@
 # flutter-webrtc-server
 A simple WebRTC Signaling server for flutter-webrtc and html5.
 
+## Usage
+- Clone the repository, run `npm install`.  
+- Run `npm run` and open https://localhost:8086 to use html5 demo. 
+- If you need to test mobile app, please check the [webrtc-flutter](https://github.com/cloudwebrtc/flutter-webrtc/tree/master/example) plug-in. 
 
 ## screenshots
-Use https://github.com/cloudwebrtc/flutter-webrtc/tree/master/example for mobile.
 # iOS/Android
 <img width="180" height="320" src="https://raw.githubusercontent.com/cloudwebrtc/flutter-webrtc-server/master/screenshots/ios-01.jpeg"/> <img width="180" height="320" src="https://raw.githubusercontent.com/cloudwebrtc/flutter-webrtc-server/master/screenshots/ios-02.jpeg"/> <img width="180" height="320" src="https://raw.githubusercontent.com/cloudwebrtc/flutter-webrtc-server/master/screenshots/android-01.png"/> <img width="180" height="320" src="https://raw.githubusercontent.com/cloudwebrtc/flutter-webrtc-server/master/screenshots/android-02.png"/>