If you're logged on at a location that has mobile library routes set up then you'll see the option Mobile Routes in the side Navigation Menu. Under that you'll see an option to start a route. Once you've started a route, the side Navigation Menu will show options to close the route, select the next stop, select the previous stop or set the current stop. The name of the route and the stop are shown in the status bar at the bottom of the screen.
To start a mobile route:
If there are routes scheduled for today then the Today checkbox will be selected by default, and you can choose the one you want from the Route dropdown, and then choose the Stop. If you want to choose another route you can always clear the Today checkbox and then all the routes will be listed in the dropdown.
Once you've started a route, you'll see the other options under Mobile Routes.