Hey! I just downloaded Unity and I don’t want to make a island. Could anyone tell me how to make it into a city instead?
Do a search for the “make city” button 
Unity is a tool to make games of all types so making a city is going to take some time. There’s no single answer for how to do this.
make a new terrain for a start. It would be needed anyway.
Then just drag your building models ( if any) from your project window, and into the hierarchy window.
Move them to wherever you want, and enjoy!
Oh, I am working on a building generator for Unity!
So that might help soon!
Okay, thanks guys!