Sorry there isn't much more documentation. I barley have time for the "fun stuff". But you will need your phone to have some sort of internet connection (wifi would be best) and you probably want it to be plugged in. Just choose a ride from the "My Rides" or "Rides Nearby" tab. After the route appears on the "preview" screen select "Download This Map" from the menu. Go get some coffee or eat a sandwich depending on how big the route is. It'll download in the background. After it's done, make sure you select Menu -> Preferences -> Map Source -> "OSM Hosted by RWGPS.com"
This is something that you'd want to do a day or so before the ride, just in case there is a network glitch that has you start over, not at a McDonald's along the course, could take too long to download.
Have a great ride!
-Geoff