This is an example of using ArcGIS Online's OAuth 2.0 authentication protocol for logging into an external application. Once authenticated (using the ArcGIS Socialite Provider), a new user is created in the database.
You will first need to register your application with your ArcGIS Online Organization through developers.arcgis.com. Once registered, you need to setup a callback URL for OAuth 2.0 to return the user information. It should look like http://<your url>/login/arcgis/callback. Keep note of your your Client ID and Client Secret, you will add these to your environment variables.
Next, rename the .env.example file to .env and fill out your database information and the ARCGIS_* information for your registered app. For added security, also enter your ARCGIS_ORG_ID.
Once your application is registered and your .env file is completed, you can install your app dependencies with composer update.