Instructions
Play through the first level, Liberty Island, until you see a monkey on the left side of the statue. This monkey is called Henry, and he'll be working on repairing the statue.
Equip your Slingshot gadget. This is also sometimes called a Catapult or Slingback Shooter.
Hold down the right analog stick to enter first-person aiming mode. Press the right analog stick down again to cycle between the available types of ammunition. You can choose between explosive pellets, guided pellets and regular pellets. The regular pellet will be enough to knock Henry down, but if you're having trouble aiming at him, just use a guided pellet.
Pull the right analog stick back toward you to place your selected type of ammunition into the slingshot. Release the right analog stick to fire the pellet at Henry. Once he has been knocked down from the statue he will be stunned, so walk up to Henry with your net equipped and capture him.