Ride with GPS does not have an app for Windows-based mobile devices such as the Lumia series.
However, a third-party has developed an app called Cycle Tracks GPS that allows Windows phones to connect to Ride with GPS and use your routes and record rides.
Ride with GPS has no affiliation or development involvement with the Cycle Tracks GPS app.
In this example, 5975691 is the route number. Just type that number into the Cycle Tracks GPS app and away you go!