How to use Image rviz when I use SITL and Gazebo

I download the SITL, which works with gazebo together. I want to get the image from Arducopter. The arducopter equips the camera, but I do not know how to use the camera. Here are the picture s about open up SITL and Gazebo. I think when I open up gazebo, I should add something to "gazebo --verbose worlds/iris_irlock_demo.world". Which command should I add, and where. Thank you! https://github.com/swiftgust/ardupilot_gazebo http://ardupilot.org/dev/docs/using-gazebo-simulator-with-sitl.html