Because your energetic boxer puppy is going to grow up to be an energetic adult Boxer, having a good grasp of the 'lie down' command is going to be very important in the future, when an excited jumping Boxer puppy becomes an adult that can unintentionally knock you and guests flying. Being able to get your Boxer to lie down gives you control over excited rambunctious behavior when you need it, and helps the puppy to relax, calm himself, and learn important self-control. Eventually, it may even be an important safety mechanism, if your curious Boxer is moving towards danger like a roadway or the neighbor's feisty cat. Also, if your Boxer will lie down on command, you will be able to take him places where he needs to behave in a calm way, such as to public places or other people's homes. This will allow your Boxer to accompany you to a variety of places, which will make him happy in the long run. He just needs to learn a little self-control first.
You can use a command like “down” to ask your Boxer puppy to lie down. Because Boxers are excitable dogs and are prone to crouch when they lay down and then pop back up again, you will want to teach your Boxer to lay down and then roll over onto one hip with his legs out to the same side, not bunched up underneath her, which will increase the likelihood your Boxer will be up again before you know it. Puppies as young as 6-7 weeks can start learning to sit and then to lie down. Remember to use patience, encouragement, and to make sure your young Boxer pup understands what you are asking of her. Yelling at or punishing a Boxer puppy that is confused will not accomplish the task and will only upset and stress your young dog. Be clear in your commands and wait for your Boxer puppy to catch on to what you are asking.