What you could do is to create endpoints around your DB operations, such as inserting a favorite place, deleting a favorite place, or updating a favorite place. This endpoints will be called in your WP8 app. To call your endpoints you'll need to deploy your service. Here you'll find a short tutorial on how to deploy a WCF service from Visual Studio to an IIS. The creation of the service itself depends on your exact use case and how you'll do the mapping to the database (for example with Entity Framework with its code-first or database-first strategies).
As an alternative you could use ASP.NET Web API, which in my opinion is easier to use than WCF. Another advantage is the RESTful architecture of Web API. That allows you to call your service from almost all devices or platforms.