I could really use some help getting started with this scenario: sending an SMS from a MS Power Flow.  I have a Power App that needs to notify students via SMS that they have a package ready for pickup.  I have some limited experience using REST API’s and I’m struggling to complete the Authentication step.  I have created a dev app in RingCentral.  I created a JWT connected to that app.  Power Flow has an HTTP connector, but I can’t find a good example of what I need to put in the header and body.

I have been trying to use the OAuth doc here: RingCentral RingEX API Reference | RingCentral Developers, but have not got the authentication request working.  

Any help would be greatly appreciated.  Especially if you can provide a screenshot of your steps in Power Flow (minus your secrets of course).  Thank you.