When a puppy starts peeing in the house you need to immediately redirect the puppy outside to pee when you catch them peeing in the house.
When you see the puppy start peeing in the house you need to make loud noises usually and then tell the puppy in a stern voice "NO" you go outside to pee.
Then immediately take the puppy outside to pee and leave the puppy outside until the puppy does pee.
A puppy should then be praised with a treat and tell the puppy that they did a good job by using the potty outside like they are supposed too.
Just like human kids though that are potty training you should never actually punish the puppy for peeing in the house when it's potty training.
Unless the puppy is doing it on purpose.
But most times it's just because the puppy is learning where to use the potty and eventually after some training the puppy will learn to go outside to potty as long as you're consistent with taking the puppy outside to potty.
And when you see the puppy about to potty in the house again you should startle it again or just redirect the puppy outside.
Taking the puppy outside on a regular basis to potty will also keep their bladder empty enough to where they won't go potty in the house.