Console commands only.
Generally though, "player.placeatme <Id here> <Number you want spawned here>" is the usual format for generating NPC's.
For example, try spawning another lone wanderer, thier code is easiest to remember.
Try "Player.placeatme 00000007 1" This will spawn a nude copy of your character before you.
Be wary when spawning enemies, as they will spawn around you and slaughter you prompty if they are in high number. If youre spawning behemoths, pop a stealth boy before spawning them
So they don't instantly destroy you.