[Pratically no experience] Changing Abigail's mechanics?

[bieux]

I want the ghost on my mod (based on abigail) to spawn and despawn when pressing a button rather than by letting a flower on the ground like abigail does.

 

The problem is that I don't really understand how to do that, I searched for some mods with similar commands, but they're too complicated and incompatible that it's impossible to adapt to my code

 

The second problem (once the first problem is gone) is getting the ghost to link to the player, what I think I can do myself as long as I know how to solve the first problem.

 

 

Any ideas?

[bieux]

I've realized that there's no option to edit my post and that I've been terribly vague in describing what I need, So, this is my edit:

 

EDIT:

 

The first thing I need is to spawn an entity by pressing a button (let's say, Z), and this ability is exclusive of certain character on my mod. How and where do I program the ability of spawning this entity by pressing Z?