QUOTE
I'll just give an example question, and from that i'll learn what I need.
I'm not sure an answer would be enough to teach you what you need. There are two things on the bottom line that you need to know about spells:
1. You can't
add special abilities to units with EUD, that is beyond the capabilities of EUD.
2. Not only that, most special abilities require that the unit graphic is already capable of casting spells, or else as soon as the player attempts to cast the spell, the game will crash. (This rule can sometimes be bent by an experienced modder)
So, you can't do what you want directly. But, I'm sure you've heard this story before. StarCraft just doesn't do half the stuff we want, in both mapping and modding. When StarCraft doesn't do what we want directly, that's when we need to get creative.
DT_Battlekruser was being creative there. The way he's suggested is the easiest way to give stimpack to a Zergling. That is the easiest way in this case. It's not the only way though, I might've tried changing the burrow order for example.
Had you asked how to do a different spell, chances are you would have got a completely different answer. That's because rule number 2 up there gets violated by most special abilities when you're talking about a Zergling spellcaster, forcing us to think around that. Stimpack is one of the exceptions that does not violate rule 2.
In general, what I'm trying to say is, there's no global set of steps to give a unit a special ability that works in every case. It all depends, and sometimes it's impossible. StarCraft is hard to mod just like it's hard to map because it constrains you and forces you to get creative. But that's what we have to live with.
Now, for the most part, getting creative about how to mod a special ability onto a unit is really only something that can be done by someone who has modding experience. You need to understand the system before you can come up with useful ideas on how to change the system. So, from here you can either do one of two things:
1. Ask more questions about specific spell that you really do want to add to a unit or
2. Learn modding.