...and your problem is?!
When asking for advice, please be specific and give as much information as possible. The problem may be clear to you but remember you are talking to people who have no idea of your project or what you are trying to achieve. To put it bluntly, if you want folks to take time to answer you, take time to describe your problem.
1. switch off all the layers intended for camera 2 - so you just see the layers intended for camera 1.
2. Add the camera and set it up.
3. Now precompose all the visible layers and the camera.
4. Now switch all your camera 2 layers back on.
5. Add the 2nd camera and set it up.