How to create a Facebook app for the Facebook Link extension?
As it’s mentioned in the installation guide of the Facebook Link extension, it is necessary to create a Facebook Link application first of all. So login to your Facebook account and go to http://developers.facebook.com/setup/.
Here please define your web-site name, site URL and locale. After that, please click the Create App button. That’s all - your Facebook application has been created. Now all that you need is to copy the App Id and App Secret values, and paste them into the appropriate fields in extension settings: Backend » System » Configuration » aheadWorks Extensions » Facebook Integrator » Facebook Settings.
Now everything is set up and your visitors can login to your store through their Facebook account credentials.