Owl's can be found throughout the game and are first discovered within the Seed Bank, moving boxes from A to B. This would be your first opportunity to get the achievement by throwing boxes at them as they go about their business.
To use Telekinesis, simply tap
to pickup an object then once in your hand hold down
to charge the Telekinesis shot. Let go of
to throw the object.
It'll take you 2-3 hits on an Owl to down it and unlock the achievement. Don't worry if you've missed them at the Seed Bank, theres plenty more opportunities to do this. Such as my example in the video below: