When your dog knows the release cue and how to sit on cue, put him in a sit, turn and face him, and give him a treat. Pause, and give him another treat for staying in a sit, then release him. Gradually increase the time you wait between treats (it can help to sing the ABC’s in your head and work your way up the alphabet). If your dog gets up before the release cue, that’s ok! It just means he isn’t ready to sit for that long so you can make it easier by going back to a shorter time.
It's important with all dog training but especially with young puppies to use lots of encouragement, praise and rewards (positive reinforcement) in your training. Start your puppy training sessions as soon as your little puppy arrives at your home - it's never too early. Set your puppy up to succeed, concentrate on developing desirable habits in your puppy and preventing undesirable behavior. It's much a better alternative to put your puppy on the right path from the start, rather than trying to correct established problem behaviors later on.
Make the puppy come to you. While he’s on his way to you, still wearing the leash and collar, back up a few paces and then reward him when he gets to you. Continue the progression until your puppy, upon hearing the cue noise, comes to you and walks with you a few paces. Remember that puppies have a short attention span, so keep your sessions short, and end them when your puppy is still eager to do more, not when he’s mentally exhausted.