After importing a non-spatial model, the next step is to import an image of the compartments in the model to define the geometry.
To do this, go to Import->Geometry from image or press
Alternatively, go to Import->Example geometry image to use one of the built-in example images.
Then you can specify the dimensions of the geometry image, and optionally reduce the resolution of the image or the number of colours to be used. The geometry image should be segmented such that each compartment has a unique colour.