The application should only be visible to who become Fan of this page. When the user becomes Fans can participate in a competition by simply filling out a form with  email. After the user submits the form, the email must be registered on a database and he can has the opportunity to publish a post on their wall (the action must be recorded on the database) and be able to ask his friends to participate in the application (the number of friends invited must be registered on the database).

For any question I'm available.