Ordering a unit to cast a custom ability

Ordering a unit to cast a custom ability

How can this be done ? Do i have to rename one of the root abilities with all the stats in the way iu want? I want to use a custom ability.

if u for example order a unit to cast 'tauren chieftain - shockwave' it casts Every ability that is based on it

And is there a way to order a unit to cast an ability that is not withing the list there ? e.g blizzard is not among them not to ask if custom can be ordered at all.

blizzard is among them, but in the 'target point'
'target unit' is for storm bolt and stuff

Working now, thx.