This tutorial assumes you have already created a graph with a diffuse output, part of which renders a height map, which may be used e.g. to compute a normal map, or as an input for an emboss filter.
To simulate Ambient Occlusion create an FXFilter to FXMap box and use it to convert your height map into an Fx-Map. Then parametrize a HSL filter with it and apply it on your diffuse map. Invert the HSL filter gradient (i.e. make the black gradient key white and resp. the white key black) and move the luminance slider on the left according to the amount of light you need.

To obtain a more scattered effect, you can also blur the height map by passing it through a new uniform blur filter before the FXFilter to FXMap.