Depending on how you've set up your game there's different ways to do this. But first, let's get some fundamentals out of the way. Local parts are only shown to a specific player, however this also means that the server is not able to see them. Only local scripts will be able to access local parts.
If you've made your game using FilteringEnabled then it's much easier to do. Filtering stops any change the client makes being seen by other players or the server. This means that you can add new parts from a local script and parent them anywhere without them being seen.
If you're not using FilteringEnabled then you have to put all parts within the Camera object which you can retrieve (in a local script only) from the CurrentCamera property of Workspace. Please note that there have been reports of certain bugs happening with this and that local script WILL NOT run in the current camera.
Best of luck! |