Cannot launch Simulation for ROS Developers Class #57


I am having trouble launching the simulation for the class #57. I have tried using the roslaunch shadow_gazebo main.launch but it doesn’t seem to be working.

This is the message that I am getting on the web shell.
[main.launch] is neither a launch file in package [shadow_gazebo] nor is [shadow_gazebo] a launch file name
The traceback for the exception was written to the log file.

Can anyone please tell me in detail how to launch the simulation? I am beginner to ROS and would greatly appreciate your help. Thank you!