Puppy and leash walking
The puppy probably won't understand what the leash is at first and will try to pull it or play with it - which is perfectly normal. That's why it's a good idea to get your puppy used to the leash as a puppy. It will be safer both for your puppy and for your surroundings when you have a dog you can control and that doesn't "run away" and pull too much on the leash.
How do I do this? Start by training your puppy indoors without a leash - the aim is for it to stay close to you only. Reward the puppy with dog treats and praise, so it understands that by staying close to you, there is always a chance of getting something good. Then walk a short distance away from the puppy and call it - reward it immediately when it obeys and comes to you. The next step is to put it on a leash and go for a short walk around the house when it's on a leash. It will take a while for the puppy to get used to it, which is the goal of the first time you use a leash.