If i want to make an aura that affects enemy units do i have to use triggers to make it or is there a way to make it in object editor? (i dont know how to make an aura in object editor that affects enemy units)
depends on your effects but no you don't trigger it; it's under the targeted units. You just select enemy instead of allied/frends and that aura will affect enemies and any other unit you checked off for it to effect.