Where and how to learn ignition for doing real world simulations?

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I am starting to build a world for ROS2 with Gazebo but I don't find real useful info for knowing the basis of this. I have build in the past simple simulation of robots configuration in ROS1 but I find it difficult to know where to find useful info for building a world with its different textures and so in ignition. It would be really helpful for me to know some resources just to start in this project. If could please help me a little bit.