Create a Facebook Application
To use fabEE you must create an application within Facebook. The process is straightforward but you must follow these instructions carefully because if you make mistakes here then fabEE will likely not work correctly, if at all. Throughout this documentation we are referring to a Facebook application. We really mean your site but that is how Facebook describes it.
Step One
Log into your Facebook account and then go to http://facebook.com/developers/apps.php. You should see something like this:

Go ahead and create a new application. You will be asked to provide a name for your application and agree to the Facebook terms and conditions. I recommend that the name you use is the same as your ExpressionEngine site but that is not required. Next you will be presented with the application configuration screens.
Step Two

You'll see that the API Key and Secret are listed at the top of this page. These values should be transferred to your fabEE settings.
You will now have to configure the application appropriately. There are seven pages of configuration though you only have to worry about a small subset of them. Each configuration line has some help text associated with it. Most items should be self-explanatory so we’ll address the configuration items that need to be explicitly set.
Step Three

Select the checkbox that allows your application to be installed by users. Then place your site domain followed by a fabEE action in the Post-Authorise Callback and Post-Remove Callback URLs. fabEE uses it’s actions as well as the standard EE ones i.e. ACT=10 for logout.
For the Post-Authorise Callback use your site domain with the fabEE 1 action. So, if your domain is mysupersite.com then you would use:
http://mysupersite.com/?FABEE=1
Use the fabEE 2 action as the Post-Remove Callback:
http://mysupersite.com/?FABEE=2
We can ignore the Profiles and Canvas settings.
Step Four

This is where we tell Facebook Connect which domain our application is on and how to find the xd_receiver.html file that is in the download package. The Connect URL should point to your site root i.e. where your xd_receiver.html file is located. Without this, fabEE will not work at all. The Base Domain setting tells Facebook Connect how it should set up your cookies. The tip to the right of the setting field provides more information.
Okay, you can skip the Widgets section. You have nearly finished!
Step Five

Now you need to make sure that your Application type is set to Web.
Step Six

Make sure that the New Data Permissions option is enabled. You have now finished setting up your application on Facebook.
In the Advanced section there is an option to enable Sandbox mode. You may wish to do this whilst setting up your site. This option removes the ability for other users to access your application (your site) and hides any comment posts you may make whilst in development. Just be sure to disable this option before launch!
You should now have saved your extension settings and be ready to set up your templates.