The Appendix gives you a quick introduction to MRST. We start by explaining how to download, install, and get started using the software. We also discuss the release policy, terms of use, and how the software has been organized into a small core that offers basic functionality and a large set of add-on modules that implement specific solvers, simulators, and tools. We briefly review all modules that are part of the 2018a release. The final two sections discuss rapid prototyping using MATLAB and MRST, present some powerful constructs you can use to speed up your MATLAB code, and explain the key ideas of automatic differentiation and how it has been implemented in MRST. Altogether, this Appendix should provide you with enough knowledge of MRST so that you can effectively use the software to further your understanding of the material presented in the main part of the book.