Need help with cameras

So I am trying to record a gameplay trailer for my game, but I want it to be gameplay in the actual game, but I dont at the same time. So I am wondering how to set up a camera that I can monitor the whole time to detect the gameplay. Dont understand? Well, ill show you what I mean. For example, . The PUBG trailer is people playing the game, but the camera is moving down the hallway, that I want to happen. I want people to be playing the game, but I want to be able to move the camera where I want it while all this is happening. How do I do this?