You use the Material Editor to apply a material to objects.
To apply a material to an object, do one of the following:
Applying a material overrides any previous material assignment the object might have had. Once the material is applied, while the sample slot is active, the material is "hot" and changes you make to it affect the object automatically. The page "Material and Map Nodes in the Active View" has a section that describes "Hot and Cool Materials."
The Undo command works for material assignment.
You can apply only one material to an object. To overcome this restriction, use a Multi/Sub-Object material. This is a container for various sub-materials that correspond to specified sub-objects such as different faces in a mesh, NURBS surfaces in a NURBS model, and so on.
You can apply the same material to multiple objects in the scene.