Blazor server and app

Hi, I have a blazor server side app ( core 3) with two “components”: an api and an UI.
I will secure the api with jwt token, and an user should login into the app.
In future I will access the api with another clients.
So I decide to call my api from my UI-component via http (httpclient). This is the way another client-application will be use.
For now I have registered my api in auth0. But now I have a “logic” problem? Why I can login the user, and use his acces_token for an api call? Should I register an additonal app inside auth0? Here is a automatic generated machine-to-machine app, but maybe I need another type…
How I can configure then my startup.cs?
Thanks in advance!