1. Step Head over to https://www.facebook.com/about/messenger to get the messenger
There are various other tools that integrate Facebook, but this is the official one and is supposedly the smoothest way to chat via Facebook on Windows.
The messenger is also available for mobile phones. All in all, it’s a rather minimalistic messenger app, but that works extremely well in this case.
What tools are you using to stay in touch with your friends? If you are bored of running multiple tools, an all-in-one solution like the Digsby messenger is a possible alternative