Try nursing in a dim, quiet place to minimize distractions and keep baby calm. If you're still having trouble, you'll either need to get creative or wait until your child is a little more chilled to begin a nursing session.
Many moms find that their older babies or toddlers have a rogue hand that waves around, pinching, grabbing, pulling, and poking whatever is in reach. It might help to occupy that hand in one way or another. So try wearing a sturdy "nursing" necklace that can be tugged without breaking, or occupy those tiny fingers with a small toy or your own hand. The perfect distraction is one that keeps baby where you want him.