To send a picture on WhatsApp using Twilio and Python, you need to have Python 3.6 or newer, a Twilio account with a free trial or paid plan, a smartphone with an active WhatsApp account, and access to the Twilio WhatsApp sandbox. The sandbox allows you to test your application before requesting production access for your phone number. To start, connect your smartphone to the sandbox by sending a WhatsApp message with a join code, then set up a new Python project with virtual environment, install required packages, authenticate against Twilio services using environment variables, and send a picture message with Twilio. The process involves creating a file named app.py with the necessary code to initialize a Twilio client, create a message instance, and send a WhatsApp message with an image URL.