Hi how can I do to make an npc and make it look like a ghost?

I asked this a while ago, and while I have yet to test it (I will literally within like an hour), you should just have to attach the default ghost script to them. The script is called something like 'DefaultGhostScript' or something simple like that, and attaching it to an actor should make them look like a ghost. In addition you should check things like 'Is ghost' in the base data of the actor window.

dos it have to be an alias in the quest or a different npc like NPC XX_Ghostversion?

Well what do you mean by ghost? I'm simply talking appearance. Attaching that script should (again it's untested) give it the blue see-through effect shader that ghosts have. If you mean a legit ghost of someone who died, there is no simple way of doing that. You just need to script and package them like the person, or however you intended.