Initializing XLabs services in WP 8.1

I'm trying to get up and running with XLabs. I installed the latest pre release across all VS projects. I'm stuck on step 1 on https://github.com/XLabs/Xamarin-Forms-Labs

It says

var app = new XFormsAppWP();
app.Init(this);

should be added in App.cs

Where do I add it exactly? In OnLaunched? Also, the Init() method expects a parameter of type System.Windows.Application. I'm getting:

"Cannot convert from XForms.WindowsPhone.App to System.Windows.Application."

I have a feeling XLabs doesn't work with 8.1 Store apps. Is this correct?