Simulation and virtual experiments are important stages of robotics research. Robotics simulators allow testing new hypothesis and algorithms without taking risks to destroy valuable hardware. Therefore, most of popular robots are sup-plied with simulation models from their makers or associated research groups. This tutorial paper describes a process of creating of a robot model for the Gazebo simulator starting from the model construction and physics setup, and ending up with sensors and Robot Operating System based control integration. The process is illustrated with an example of a step-by-step modelling of a crawler-type robot Servosila Engineer supplied with an open-source code via a public Gitlab repository.