The example is pretty straight forward. The code you actually need (TurboActivate.cs) can be added to any app or Service (including WPF). Just add the file to your project and follow the Using TurboActivate with C# article.
Example of errors,
void ShowTrial(bool show){lblTrialMessage.Visible = show; // giving errorbtnExtendTrial.Visible = show; // giving error
mnuActDeact.Header = show ? "Activate..." : "Deactivate";
That's not part of the API. That's just showing one way to show trials. Obviously it would be different for your app. And since WPF controls don't have boolean "Visible" properties then you'd have to modify that code to fit your app.
Does that make sense?