A simple question about issueing orders

I don't understand how you issue orders to tell a dummy unit to cast a spell. All I see are existing spells, like "ArchMage - Blizzard" and such. Can I have to some help?

All custom spells (with the exception of channel) carry the same order strings as their base spells. So if you based the spell off Archmage's blizzard (or any blizzard, they all have the same order string I believe), you can use ArchMage - Blizzard to cast that spell.

Oh, didn't know that, obviously. Thanks!