I figured all I had to do to make flying enemies was attach a set of wings to them, but doing so just turns them into hopping enemies, not flying ones. How do I make flying enemies? Is there a separate item for it, or is there something special I need to do in order to make the "hop wings" into "flying wings"?
You should have a Wing item in your tool bar; it just looks like a white wing. Simply drag that onto an enemy to attach them and make it fly.
Each enemy has slightly different behaviour with wings attached. For enemies that bounce around instead of fly, try placing them in Lakitu's cloud or the Clown Car.