Hello Hassan,

You'll want to begin at the beginning (if you have not already) by visiting the Developer Portal (https://developer.ringcentral.com) and going through the Quickstart Tutorials so you can familiarize with how to properly setup and begin developing with the RingCentral API.

Once you have completed that, you are going to want to use one of our SDKs (because they simplify the developer work needed to operate with our API). Using these SDKs, you will want to create a Subscription, and monitor Presence events for the various extensions in your RingCentral account you care to monitor. Our API Developer Guide has the complete details on the spec for creating each of these objects in your code to achieve your desired use case.

I have created this repository on Github using our RingCentral JavaScript SDK to demonstrate the basics of how developers can use the Push Notification (Subscriptions/PubSub). Please feel free to fork this code into your own repository and follow the directions in the README.md file to get it up and running. If you have any questions or issues operating this code, please add these in the Github Issue tracker for the repository.

---