Adding magic animations isn’t as simple as battle animations. Vanilla magic animations are pretty hardcoded, so you can’t just drop them from one game to another, unfortunately. There are some custom magic animations that exist, but they were made using a completely new system from the vanilla ones ( [FE6/7/8] Circles' Spell Animation Creator [UPDATED TO V1.1] to be specific).
So, to get those magic animations in FE6 you’d have to recreate them in CSA Creator format, which would take some work.
If you’re lucky, some people might have already done so - check the repository ( https://emblem-anims.herokuapp.com/ ).