I would suggest getting a good book on dog obedience training.
This is so that you can be trained how to train a dog.
Once you got that down pat be consistent on your tone of voice and what you mean when you communicate with your dog.Like No is no and YES is yes.
The hunting part, some dogs will take it naturally some have to be tutored.
You can tell a natural flushing puppy will like to chase Robins or other birds in the field.
You can encourage this on walks. If you have a friend who have a good flushing dog try to apprentice your dog with this good hunter on field walks.
Retrieving.... Most labs are natural retrievers and all you do is encourage them to bring it to you.Do all the serious stuff like come and retrieving with a CHECK CORD to let the dog understand you have control at all times, when your voice say so.It should be light enough that he won't notice the difference whether it's on or off with him having a collar all the time.
Trailing... with a dead game you can drag an unseen trail and let him find it by following
the scent, once found the same bird can be used for retrieving training.
Flushing game...with a live bird drag a scent trail which ends up on bird in a trap.The trap has to have a means to open the door when the dog is there so he can see it fly away, when he is very close.If he catches the bird that's fine.It will at least teach him there is a bird at the end of the scent.
You can start with the fun and games to simulate hunting anytime just don't make it too serious that he will lost interest.Always end any training with fun play.
Introduce noise ... while he is busy or playing to prepare him to the sound of gunshot later.I hope this helps.
Good luck,
louie