Click the Create Application button.

Sign up for a free Auth0 account here.

Add the name "React Code Sample" and select "Single Page Applications" and the application type then click Create

Click on the Settings tab of your Auth0 Application page, scroll down to "Application URIs" section, and fill in these values:

Allowed Callback URLs http://localhost:4040/

Allowed Logout URLs http://localhost:4040

Allowed Web Origins http://localhost:4040

Scroll down and click the Save Changes button.

On the "Basic Information" section get the Auth0 Domain and Auth0 Client ID values and paste them a .env file in the root of the project.

REACT_APP_AUTH0_DOMAIN=AUTH0-DOMAIN
REACT_APP_AUTH0_CLIENT_ID=AUTH0-CLIENT-ID
REACT_APP_AUTH0_CALLBACK_URL=http://localhost:4040/