I need a little help for including a simple button to an existing facebook site on my mainpage. I've read this exchange on adding a facebook widget, but something is missing:

Adding Facebook widget to site

It's quite simple to go to the catalogue and select a facbook widget. I don't know what the difference is between badges or plugin widget is, so I just took the latter.

The window "Create new widget Facbook social plugins" appears where I could insert the code, but where to find it? What's the next step ?