From Facebook Developer Wiki

A basic Smalltalk library has been created using Cincom's VisualWorks - the library should be easily portable to other dialects, such as Squeak. To get started, you'll need to download the latest version of VisualWorks - you can do that here.

Once you have VisualWorks installed, you'll need to connect to the Public Store Repository. You can do that directly from the Store menu (read access only) without getting an account. Load the bundle named FacebookBundle.

For more information:

The Facebook Connect page at Cincom Smalltalk

Getting Started with the Facebook Connect (Screencast)

More on using the Facebook Connect (Screencast)