Allows you to display the feed of a public page or profile on your website. Requires that you create a Facebook Application.
First you will need a Facebook account, then you must register as a Facebook Developer at http://www.facebook.com/developers/apps.php where you can then create your Facebook application. After you create your application you will be given and App ID and Secret.
One way is to go to one of the photo albums from your Facebook page or profile and look at the URL. For example here is the profile pictures album for Rehema Ministries Facebook page. * WordPress Notice in the 'set' variable of that link the last set of numbers after the last period. In this case those numbers are '101359869934470'. That should be the id of your page or profile.
My first guess is that your content isn't set to be public or you haven't provided a valid Facebook page id.
Because you have either supplied an invalid App Id & Secret combo or you're trying to access something you don't have permissions for.