Make sure that you have created an app in the RingCentral Developer Portal. Make sure that this app has permission "WebSocket Subscriptions". If you do not know how to do so, please create a new ticket here: https://developers.ringcentral.com/support/create-case
Rename .env.sample to .env and edit it to specify your app and user credentials.
In your C# IDE, configure the project to copy the .env file to output.