Thanks for your question. However we ask that you please ask questions on
http://answers.ros.org following our support guidelines:
http://wiki.ros.org/Support
ROS Discourse is for news and general interest discussions. ROS Answers
http://answers.ros.org/ provides a forum which can be filtered by tags to
make sure the relevant people can find and/or answer the question, and not
overload everyone with hundreds of posts.
[However, you might want to check out http://wiki.ros.org/urdf/Tutorials/Using%20a%20URDF%20in%20Gazebo]