Download NPC Populator Free Unity.
The NPC Populator for Unity makes it easy and quick to add many free-roaming Non-Player Characters to your environment without writing any code. Only some configuration is necessary.
Included is an NPC Factory to automatically generate random humanoid NPCs based on humanoid models that you provide — many from the Asset Store will work — and scripts to animate your NPCs while they navigate through your environment.
Navigation uses Unity’s Navigation Mesh system along with a waypoint system that is provided by the NPC Populator.