Integrating Ionic User Service with back-end authentication

I’ve read Ionic User Service docs and now I want to use it in my new Ionic 2 application, that needs to consume an API secured by JWT token.

In the past, I used Satellizer to handle authentication flow. There were /auth/facebook and /auth/google endpoints in the back-end that received, after successful authentication, a code to validate and get more information about the user through Facebook and Google+ API and returned a valid token.

How can I do the same with Ionic User Service?