First of all puppies should love puppy school so if there is one close to you take your puppy there. If you don’t want to take your puppy to puppy school you can train it like this:

First, you need puppy treats or else your puppy will not do what you want it to.Then you need to get your puppy outside and say firmly “sit” while you hold the treat up high so the puppy can’t get it but it is still visible by the puppy.You keep doing that until the puppy does what it’s told and when it sits then give it the treat.