Authentication, Node Express with React

Hi all, I’m really in trouble for understand how manage authentication with React and Express, I’ve an Back End API with a passport local and an Front with React.
Someone can help me how to do that ?

Do you have a code? any screenshots? this is kind of vague

You can see the github of front:
in my front I’ve created a form for log in, but after I don’t know how to manage the session, I can store the username in a state, and another state like “logged: true” in react but what if accidentally the express app log out the user ? How to transmit that on the front ?
Sorry for my english, I hope your undestand me