This tutorial guides users through building a WordPress plugin called Sendex that allows them to send bulk SMS. The process begins with installing WordPress and creating a Twilio account, which provides the necessary credentials for sending SMS messages. A WordPress plugin boilerplate is used to create the basic structure of the plugin, including settings pages and functionality for sending messages. The plugin includes a form for users to enter their API credentials and a page for sending messages, where they can input the recipient's number, sender ID, and message. The plugin uses Twilio's PHP library to send SMS messages. With the plugin installed and configured, users can test its functionality by sending messages from within WordPress.