Wpf Service Application

First of all, why would you entangle WPF and WCF in this question? These things are unrelated, don't mix all things together. Ever heard of separation of concerns? Please see:
http://en.wikipedia.org/wiki/Separation_of_concerns[^].
 
Besides, even though you can host a WCF service in a windowed or other interactive application (again, it does not matter if it is WPF or not), this is not an adequate form of application user as a service (but it's a good idea to have such interactive version of the same application, as debugging is a whole lot easier). The adequate form of application hosting any kind of services is the Windows Service:
http://en.wikipedia.org/wiki/Windows_services[^],
http://msdn.microsoft.com/en-us/library/ms685141.aspx[^],
http://msdn.microsoft.com/en-us/library/d56de412%28v=vs.110%29.aspx[^].
 
Now, how to use WCF? I would advise to use WCF self-hosted in the service application. Please see:
http://msdn.microsoft.com/en-us/library/ee939340.aspx[^].
 
To understand how can it look along with the clients, please see this article on WCF hosting and consuming:
http://msdn.microsoft.com/en-us/library/bb332338.aspx[^].
 
This should be enough to get started. For some good code sample, you can also perform the CodeProject article search. But not mix it with WPF.
 

—SA