How do I make the Player fly upwards when a button is held, but fall when it's not?

I want to make my character fly upwards when a button is held (animation then plays) and fall when not held (animation reverts to Idle).

How would I go about coding this?

My player has the Scroll-To and Platform behaviours.

Animation is then displayed

I should probably explain that the Animation is an add-on, and doesn't actually convey the flying.