The new web client is an extension of the data from your phone, displayed in the browser. It’s very simple to set up, and as long as your phone is connected to the Internet, you’ll be able to send and receive messages via the Whatsapp service right from your PC.
First you need to Go to web.whatsapp.com on your browser. Then you will see a QR Code and you need to Scan it to pair you phone with the PC. Before you try this, Make sure to install the latest version of WhatsApp on your phone.
This feature is available for Android, Windows Phone and Blackberry devices, but it is Not available for iOS devices due to the limitations on iOS.
The Web Service will also Only work with Google Chrome as of this time, but that might change in the future.
Did you try it yet? If not give it a shot right now, and share this with your friends so all of them will be able to set it up.