I'm on holidays right now, please excuse the rather short reply.I suggest you look at the Quick Start Guide again.
You will need:
- a DEM. SRTM will always work but if you are slightly more ambitious, you can go for USGS NED DEMs, for better resolution. You get them the via the USGS National Map Viewer.
- raster maps. Easiest way is to use the TransDEM map tile client and Open Street Map as a provider. Open Street Map will tell you where the railroad is. Actually, it's easier to start with the map and then find the matching DEM for it.