Open map, select a course (some of them have more than one), then from bottom left start simulator.
You can also use your own maps and courses. Just open them in 2d.routegadget.net, export map area in question (about 2 x 2km) as jpg with print/export button (you'll long name with coordinates in file name). Also click course with the course drawing tool and export it as a gpx file using the export button below the course tool. Then zip exported map and course gpx together and open the zip in 3d. You should then be able to run/play it in 3D.
Simulator is somewhat playable also with mobile device, at least android phone. Slide you finger(thumb) on top of the controller area at right hand side.