Assuming you are using an aiStandard Shader -
- Create a Maya 2D File Texture node
- Create an Arnold aiNormalMap node
- Double-click on the Maya 2D File Texture node, and when it appears in the Attribute Editor, load your Normal Map in the "Image" slot. In the Attribute Editor, find the "color space" setting and set that to "Raw".
- Connect the "output" of the Maya 2D File Texture Node to the "Input" of the AiNormalMap node.
- Connect the "Output" of the aiNormalMap node to the "Normal Camera" input of the aiStandardSurface shader.
That should do it. A few notable details:
1. The aiNormalMap node is set by default to read tangent-space normals, you shouldn't have to do anything with it. It does have an "intensity' setting, which allows you to fine-tune the effect of the map. You should leave that alone until you need to fine-tune; you should be able to see the effect without touching that setting
2. A normal map disturbs the way in which the camera interprets the surface direction, an illusion that is enhanced by light and shadow. it's best if your shader has at least a small amount of specular reflection; this will enhance the effect of the normal map.
3. Also note that normal mapping does not work with the Maya software renderer. You should be using an Arnold material. if you use a Maya Blinn or Phong material, you'll need to use a Maya "bump2d" node. Connect it as you would any bump map, but set the "bump type" to "Tangent Space Normals". You're much better off using the Arnold aiStandardSurface and aiNormalMap nodes described above.
