How do I assign a second camera to a shot?

To shoot two shots at the same time on different cameras, just add/move the second shot to be immediately after the primary shot. Open your first shot and select "Link With Next" under Shot Settings. The two shots will then be linked, moving together and sharing the same estimated time. You can also assign camera letters under shot settings. 

By creating separate shots and linking them, then labeling the Camera Category A, B, C etc you can clearly show what each camera is to capture.