Question about Displaying camera

Ok i looked through the forum and didn’t see any threads that seemed to have the same question as me so my question is, How do i make it so when I spawn a display, like the flatscreen TV in useful and explosive props, that it shows what a camera I spawn is showing. i have seen it done on servers, and i didn’t have to mess with anything, so is there an addon I need? if so could someone tell me the name of it, or tell me how to set it up that would be greatly appreciated. thank you =D