This textbook covers the framework of first-principles analysis applied to materials using density functional theory (DFT). It provides a set of hands-on tutorials using the Quantum ESPRESSO package, an open-source software for DFT. The tutorials are well chosen, designed for maximum effectiveness while requiring a minimum of the reader's time, and the book describes how the essential components are combined to create the practical applications based on the idea of modeling practical problems of materials. The book carefully explains how to prepare the platform to run the tutorials assisted by free software. This textbook is useful for students in experimental laboratories, for industrial researchers, and for those not majoring in theoretical studies but learning individually.