For activating the visualizer, with any example, just pass the option --SimulatorImplementationType=ns3::VisualSimulatorImpl to it, assuming the script uses ns-3's command line parser (class CommandLine), and add 'visualizer' as a module dependency to that program. Alternatively, run the example with ns3 run adding the --visualize option. For example: ./ns3 run wifi-simple-adhoc-grid --visualize