ns-3 is build in Python and C++. Here are the main simulator phases which you have to specify:
- Define the network topology.
- Develop your models (e.g. UDP, TCP).
- Configure the nodes and links.
- Simulate network events.
- Analyze performance of the simulation.
- Visualize the results using plotting libraries.
Download the official ns-3 paper here to learn more about the ns-3 simulator.