To send WhatsApp messages from a Java application using the Twilio API, you need to install dependencies such as Java SE version 7 or higher, a free Twilio account with an activated WhatsApp Sandbox, and the Twilio Java Helper Library. You also need to set up your development environment and obtain your Account SID and Auth Token. The Twilio Java helper library is used to send messages via the create method of the Message class, which requires the sender's and recipient's phone numbers and a message body. Once you have installed the necessary dependencies and obtained your credentials, you can compile and run your Java application to test sending WhatsApp messages using the Twilio API. With this tutorial, you can also explore further tutorials on receiving WhatsApp messages programmatically, using messaging templates, and learning more about the Twilio WhatsApp Quickstart Docs.