For bump-mapping you can use a black & white image-map as a bump-map with a Bump-node (vector -> bump). From the Bump-node the noodle goes into the Diffuse and/or Glossy Shader Normal input.

An example of a bump map node tree.
An example of a bump-map node-tree.

When using the bump node-tree as a normal map you should first change the noodle from the Bump input from Height to Normal.

Instead of height use normal.
Instead of Height use Normal.

Next you can connect the Bump output Noodle to the Displacement input of the Materials Output. In this case I used a Multiply noodle to have some control over the Normals strength.

todisplacement
Controlling the normals strength.

 

Using a bump-map as normals in Blender cycles
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