Well the facebook object is pretty self explanatory.
You add the facebook object.
If you then click on the facebook object whist its in your objects panel(By default, The right hand side), Then look to the properties bar(Left hand side) it will ask for your APP ID, This is given you by facebook when you create a app.
To create a app you need to go to developers.facebook.com and create a app.
Now to use the facebook plugin, call a event like,
Button - on click
- facebook - login
This is now set up so you can use the users facebook in your game,
So now you can publish to stream or scores ect, Just play around with it.
Note it will only work once exported, uploaded to a server then give the correct directory to facebooks iframe..