Well, what exactly do you want to do?
You can:
Create a new pawn with a SpringArm and a Camera and let this pawn follow your NPC
And choose this Pawn as your DefaultPawn in the WorldSettings/GameMode
OR
Create a Springarm with a Camera inside the NPC blueprint and do this in the level blueprint (NPC must be in the level to do it like this):
For this you have to choose None as your DefaultPawn in the WorldSettings/GameMode