Need to Sign in single step for embeddable widget which is browser based and private

The embeddable does not support password flow authentication. That is why it requires the app to be "browser based" and uses authorization flow authentication.

Any embedded or browser based application will always have Authorization Code flow which is more secure and provides better security and you need to follow that steps.

"RingCentral supports the Authorization Code flow for apps that can protect a client secret and Implicit Grant flow for apps that cannot (e.g. a browser-only application). "

Here is full details:

https://ringcentral-faq.readthedocs.io/en/latest/oauth/

ok thank you.After signing in i am not getting auth token in my control.How to get auth token in my application to hit APIs in my web application.