You can apply materials to model elements in any of the following ways:
By category or subcategory
In a project, you can apply a material to a model element based on its category or subcategory.
By family
In the Family Editor, when creating or modifying a component, you can use family type parameters to apply a different material to each piece of geometry in the component.
To apply materials to system families elements, see Applying a Material by Element Parameter.
By element parameter
In a project, you can select a model element in a view, and use element properties to apply a material.
By face
In a project, you can use the Paint tool to apply a material to selected faces of model elements. See Applying a Material to the Face of an Element.