Make people appear out of nowhere

Hi. I'm a student and I have this idea for a project where someone is standing in a stationary spot speaking and people begin to pop out of nowhere around them. This is a fixed camera, single shot clip. I've searched for hours and watched countless Youtube videos and can't seem to find what I'm looking for. Does anyone have any tips they could offer? I'm pretty new to premiere pro, so any help would be really appreciated. Thanks!