If you want to chat via Google chat you must login into Gmail or Google chat desktop programme. Chat for Google is a Google chrome extension that will help you to chat in your browser. You can easily install on your chrome browser.
After the installation of Chat for Google you can see icon on icon tray. Simply click on the icon and login into your account .You will get all features in Gmail. You can quickly launch Google+ Hangouts.
Downalod Chat for Google click here.