Base Textures

In the base textures panel you'll find the base textures of your material. These include a normal map and an ambient occlusion map. They will be overlayed over all other layers.

Normal

To use the normal map, enable the checkbox and open up a normal map. Then you can change the strength of the map.

Ambient Occlusion

To use the ambient occlusion map, enable the checkbox and open up an ao map. Then you can change the opacity of the map.