The guide outlines a process for receiving SMS messages on a LinkIt ONE using Programmable Wireless, AWS IoT, and Lambda. It starts by setting up an API Gateway mock endpoint to receive incoming messages from Twilio, which triggers a Lambda function to publish the message to an MQTT topic subscribed to by the LinkIt ONE. The Lambda function extracts key information from the message and sends it back to the LinkIt ONE for processing. The guide then covers setting up IAM permissions for the Lambda function to publish to the MQTT topic, building out the API Gateway mock endpoint with a Lambda integration, and deploying the API to production. Finally, the code provided demonstrates how to handle incoming messages on the LinkIt ONE using the Twilio message handling callback.