To send a WhatsApp message, start by opening the app and navigating to your contacts or chats screen. Select an existing chat or tap the new chat icon to find the contact you want to message. Type your message in the text box at the bottom of the screen. You can also add media such as images, videos, or documents by tapping the attachment icon. Once your message is ready, press the green send button to deliver it. WhatsApp also offers voice messages, which you can send by holding the microphone icon. The app makes messaging fast, simple, and convenient.