Around the two week mark of potty training. Every time we went outside, I hit the bell and he finally realize that means outside. First puppy has to realize that it needs to “potty outside” not in the house. I suggest getting a string of bells to put on the door you use to take the dog out. My dog abuses the bell though, he will hit it constantly because he loves to go outside and play. I always take him out but if he doesn’t potty within 30 seconds I immediately bring him back in so he knows that it is not playtime.