Hello. My name is Michael. I can help you with your question.
When you start a meeting, it should say that you have a camera and ask you if you want to use it. If it doesn't do that, make sure you have video enabled in WebEx. To do that, follow these steps:
If that doesn't help, or if the option for video isn't there, please let me know. Also, it would be helpful to have the exact working of the error you are getting.