In the Model Builder you create a model with the Model Wizard. After choosing geometry, you select physics interfaces from a tree view. This tree view contains categories representing physics areas at the top level, and possible subcategories in each Physics Area or Predefined Multiphysics. When you create your own physics interface, you can always put it in an existing category; see Physics Interface for more information about how you do this. To create additional Model Wizard entries, add a Model Wizard Entry.