As much as we want to think puppies are born to understand what a collar and leash is…the truth is they won’t get it. Most of the time, your new puppy has never even seen a leash or a collar. Dog training 101: you need a marker word that indicates to your puppy they have done something right. My marker words is YES! It is quick, easy and it rolls right off the tongue. You can choose any word like such as “nice” or “wow,” it’s up to you, just make sure you use it every time they succeed! Once you have your marker word you will then always want to follow it up with what the puppy has done right. If ask my puppy to sit (and he did) I would say “yes” “good sit”.
Collar & Leash Training
Start SLOW! The first step is ensuring they get used to their collar first. This should be done by putting it on for short periods at a time. I start by saying “collar” and then rewarding with a “yes” good collar and treat as the collar is put on. This makes the collar fun and you reaching for his neck to grab or put a collar on fun. 
Getting used to the leash can be tough so start off in a place with very few distractions. I like to start by putting the leash on inside where distractions are fewer and your puppy is familiar with the environment. Start by just putting the leash on your puppy and let him drag it around. Ensure the environment is clear of anything the puppy could get caught up in with his leash. When your puppy drags it around without having any issues reward by saying “yes” good leash and treat. Let your puppy drag the leash around a few days in small increments and ensure you are marking the behavior.
After your puppy can handle that, pick up the end of the leash and apply a bit of pressure against his collar. If he responds well, reward the behavior. Do this several times a day and then let him wander around outside wherever he wants to go. You, of course, are watching him to ensure he is in a safe area. Do this often and your pup should have no issues with the leash.
Big Leap of Faith 