In order to make an NPC you'll need: a hefty supply of body parts, voice, animations and a place far away from pitchfork-armed mobs.
Watch this #REDkit tutorial with dr Fran... Mátyás from Yigsoft and learn how to create NPCs and bring them to life!
The Witcher 3 REDkit — Tutorial #6: Creating Entities
Source: Steam Community (opens in a new tab)