The article guides users through adding login/logout functionality to a Next.js application using the Netlify Identity Widget. It starts by setting up a new project or using a starter project, enabling Netlify Identity, and installing the widget in the application code. The article then explains how to add authentication functionality, including initializing the widget, authenticating with OAuth providers, and handling login and logout events. The user can customize their experience by adding routing/redirects based on login state, custom hooks for widget functionality, styling the modal, and setting site locale. Once the project is deployed to Netlify, users can access their app's Identity Settings to add auth providers, limit registration, and customize emails sent to users.