There is a ton of videos out there and allot on YouTube. I would suggest that the first time you take the dog hunting to not drop multiple birds at one time or it might be an overload on the dog as in it's out retrieving a bird and you drop a second bird and your dog might drop the first bird to go after the second.
The biggest thing that will help you is having a dog that follows basic commands as in here, sit and stay.
Good luck and don't get too frustrated
