How to teach your dog to retreave
Choose the toy or any object that you wish for your dog to retrieve. Show the toy to the dog and let is smell it. Then throw the toy to a small distance 5-6 meters. If your dog is a retriever normally will go after it by instinct. If not then grab your dog from the collar and force it slowly to the toy. Then place the toy in the mouth and take the dog back to the start point. Repeat this several time till the dog learns to retrieve. Before you start with this exercise you can rub the toy with some dog food so it will trigger the dogs attention.