Start by downloading and installing the WhatsApp application for your Windows PC or Mac. The application is obviously free, and will allow you to synchronize all the conversations stored on your smartphone with your machine. You will also be able to enjoy audio and video calls on your computer's big screen (equipped with a webcam) as you usually do on your smartphone.
Open the WhatsApp application on your computer. The window that opens shows a QR Code that you need to scan from the WhatsApp application installed on your smartphone.
Enter one of your existing conversations, or initiate a new conversation by clicking on the appropriate button and choosing your correspondent.
In the chat window, click on the camera button to start a video call, or on the phone button to start an audio call. The call is automatically launched in a remote window. You can end the call by clicking on the hang up button as you usually do on your smartphone.