Identify what you need from the simulation.
Discover what software will get you to that solution.
Create an accurate 3D or 2D model and import it into simulation software.
Specify and input all known real-world variables. If not known, start with default values or suggested ranges to experiment with.
Run the simulation and receive the results.
Analyze results, iterate/change values, report findings to your team, and implement necessary design changes for stakeholders.