Would you like to learn more about numerical relativity and our newest simulation code, AthenaK? We have recently published an extensive tutorial showing step-by-step instructions for how to reproduce GW150914, the first binary black hole merger ever detected. The tutorial comes with all scripts necessary to compute the gravitational-wave signal from this event and to visualize the spacetime geometry, as predicted by general relativity. A detailed description of the simulations, including cross-validation with other codes and a comparison with the experimental data is contained in a companion article, just published on Classical and Quantum Gravity.