This presentation was used for the paper: https://zenodo.org/record/3562042 Software-Defined Networking (SDN) and Network Function Virtualization (NFV) technologies enable a major technological breakthrough for telecom operators' networks. In this paper, we present the NFV over IP over WDM (NIW) library, an open-source framework for SDN/NFV metropolitan networks, created in the context of the Metro-Haul project. NIW is a library added to the Net2Plan open-source network planning software, specifically to model, provision, design and evaluate SDN/NFV networks. We introduce the major components and functionalities of NIW in a tutorial manner, including an Excel file loader meant to ease data loading for its manipulation through NIW data structure and its available methods. Finally, an illustrative example shows the basic library usage taking into account NFV over IP over WDM network resources in a reference topology.