To make video calls you need to select the friends with whom you want to chat. A pop up window will open up bringing up the video chat feature. The window is re-sizable and it can be viewed in full screen mode.
Inside the app there is one small window that gets smaller when mouse is not hovering over it. This facilitates you to see yourself when you want to chat. There is no mute, hold or in-call buttons in it.
Yes, it's available now. The first step adds a video camera icon to the chat window. You will
need to choose an available friend to call by opening a chat with them,
click the video camera icon in the chat window, and then install a
plugin on your computer to enable video calling on Facebook.