You should see a list of routes and folders on left, and a list of trains on right. If either one of the lists is empty, the program needs to be re-configured.
The current folder is shown above the route list. You can change folders by clicking one of the folders shown on the list in yellow. Clicking the (..) folder moves you to the parent folder of the current folder.
Different types of routes are shown in different colors: red for rw-routes, green for csv-routes and blue for brf-routes. Brf-routes can usually have more randomized elements than the other two types.
Double click any route or train to open an information box. The information box for routes displays the route name, description and the intended train for the route. These don't necessarily work on (all) brf-routes. Train information box is quite similar, but it also shows what the cab of the train looks like, and the train itself.
After you've chosen the route and train, the 'Select' button becomes clickable. Clicking it will bring you the starting options dialog.
This is where you choose the effects you want BRR to apply on the route. BRR creates a copy of the original route, so no permanent changes are made.
Starting options
Warning!
Some routes have stations where the starter is missing, is in front of the station, or is set in another unusual way. This may cause problems like jammed signals or train refusing to leave the station.