This is an intermediate level tutorial. Before embarking on it, you should complete all the introductory level tutorials. Having completed those, you are likely to be at the stage of wanting to model your own sample.
This tutorial gives you a step by step walk-through of how to do that. For completeness, we use a new sample type, namely a highly porous (94%) mineral sample, and there is specific advice in this tutorial about how to model and view the results for highly porous samples.