Alright.. 3 of my friends have asked me already so i'll make a thread.
Most people do this through the Database but it is also possible through commands!
1. Target your npc
2. do this command: .mod bytes1 2
3. Now equip your NPC by doing: .npc equip1 <YOUR ITEM ID HERE>
So if i were to equip my NPC with a worn shortsword I would do this:
.mod bytes1 2
.npc equip1 25
Equip1 = Main hand
Equip2 = Off-Hand/Shield
Equip3 = I think bows.. not sure.