Unlike with your car, a Garmin (or Wahoo or any other cycling GPS device) doesn't come pre-loaded with maps. If you want to follow a specific route on- or off-road, you need to load it on to the unit first. That means that you need someone to have ridden the course you want to follow. If you're just talking about riding in a park somewhere, there are probably any number of routes out there. Strava lets you rip the GPX track from anyone who uses a device that supports that functionality - you can just download it and then upload that track on to your device. You don't even have to follow the rider you get it from to pull the track. RidewithGPS allows you to do that for pretty much everything they have (and in multiple formats - FIT, GPX, TPX.) I've had a pretty good experience with this - both on- and off-road. I can see where they can fail sometimes, but I've been in pretty remote areas and the track kept me in line the whole time. But I'm not aware of any cycling app that has preloaded maps of trails that will give turn-by-turn directions without you first loading an existing track.