Most material types have a Maps rollout.
Example: Special Purpose Maps rollout for the Arch & Design material
Initially the button is labeled "None."
Double-clicking the map's name in the Browser also assigns the map type.
Many material rollouts have shortcut buttons for assigning a map to some of the material's visual components. These small buttons are equivalent to the buttons on the Maps rollout. Assigning a map to a button in one rollout changes the corresponding button in the other. There are similar controls for material types that don't include explicit Maps rollouts.
Shortcut map button in a material’s Parameters rollout
In the Slate Material Editor you can also assign maps by wiring nodes.