Each component of a material has a set of controls for bitmaps. These are the same for each kind of component.
Open New Map File: Click to display a bitmap file dialog, which lets you choose the map to assign.
Note: To save loading time, if a map with the same name is in two different locations (in two different paths), it is loaded only once. This poses a problem only if your scene includes two maps that have different content but the same name. In this case, only the first map encountered will appear in the scene.
Clear Map: Removes the map from the material.
Show Map in Viewport: Turn on to have the map displayed in viewports.
On: Controls whether the material uses the bitmap, or not. When on, the bitmap is active. When off, the map is not used.
Amount: The Amount spinner determines the amount that the map affects the material. Its value is a percentage of full intensity. For example, a diffuse map at 100% is completely opaque and covers the base material. At 50%, it is semi-transparent and the base material (the diffuse, ambient, and other colors of the unmapped material) shows through.
The Amount is available for adjusting only when the map is turned on.
Procedure
To assign a bitmap to a material component:
In the Material Editor, go to that component's tab.
Click Open New Map File.
In the bitmap file dialog, choose the bitmap you want, and then click Open.
The map is now used by that component, as described in Mapping Material Components.
Note: You can't assign a map to the ambient or specular color components when these are set to match the diffuse component.
Tip: If you want the same map applied to more than one component, you can drag the checkered bitmap icon from one component's tab to another. See Component Factors.