Your Puppy Wasn't Born Wearing a Collar & Leash
It is probable that your puppy has never worn a collar or leash until the day you brought her home! Something around your pup's neck, like a collar, feels weird to her and you're likely to see her scratch at it or rub her neck on the floor or a piece of furniture in order to try to remove it. When you attach a leash to the collar, that collar suddenly gets heavier and you'll see even more fussing with it. Plus, you're likely to see your puppy "put the brakes on" when you try to take her for a walk, resulting in your frustrated attempts to drag her. All of this is because she doesn't understand the concept and feel of wearing a collar and a leash! Rather than this being a battle, help your puppy to acclimate to the collar and leash instead!
Get your puppy some great treats that are SOFT and quick to chew. Soft treats are key, especially for a puppy with little teeth that take too long to chew a crunchy treat. There are lots of treats available that are soft, and your pet professional can show you a nice assortment.
Using pea-sized treat, put on the collar and give her a treat. Remove the collar, wait a couple of seconds, again put on the collar and give your pup a treat. Repeat this 10 times so the pup can associate the collar with getting a wonderful treat.
The next session, later that day, repeat the Step 2 process but after you've put on the collar count to three in your head, then praise your puppy, give her the treat and remove the collar after she's finished chewing.
The third session, the next day, you will repeat this process but count to six, then reward. The fourth session, later that day, count to 10 before rewarding. What you've been doing is teaching your puppy to accept the feel of the collar for longer periods of time and rewarding her for remaining calm while wearing it.
At the fifth session you will attach the collar, attach the leash, count to 10 and then reward your puppy. Remember, you're still doing ten repetitions of this before ending the session.
At the sixth session, later that day, you will take a step forward after attaching the leash and reward your puppy for taking a step with you. Don't pull or drag your pup because she was born with "opposition reflex" meaning that she will pull against what pulls her or push against what pushes her. If you pull, your puppy will apply her brakes because she is using her "opposition reflex" which is a natural and normal response from her! Instead, reward your puppy for taking a step forward, then reward for taking three steps forward, then reward for making it half-way down the walk, etc.
Watch your energy, too! If you try pulling or are frustrated, that negative energy will travel right through the leash and your puppy will stop moving because she's fearful. Instead be happy and "jolly" her out of her fear. Pat your legs and encourage her with your own confident behavior, happy tone and a smiling face.