How do i make strucures load like in fortnite

Im making a game and im wondering how does fortnite make ctructure prefabs (loading a building and some area around it ) and it spawn with random loot and how do i make it out of sepreat parts

What you’re asking for is not simple and I very much doubt anyone will answer in text how to do it. There are quite a few things you need to set up, but this guy explains it all. If you have the patience to stick with it.