Just like the web version of WhatsApp, the MsgPort is an extension of your phone, which simply mirror your conversations and messages as they are in your phone device, that means, all your messages remain originally saved on your phone.
Your phone must be connected to the internet for the "WhatsApp Messenger is" to work, and in addition, make sure you have the latest version of WhatsApp is available for your phone.
To connect, open the "MsgPort for WhatsApp WA" and you will see a QR code, simply 'scan' this code using WhatsApp on your phone and you will be logged in.
You will find this option within WhatsApp settings on your phone, at "WhatsApp Web" menu.
This is an UNOFFICIAL tool for WhatsApp Messenger.