Your Pit Bull puppy is a giant ball of energy, smashing around your house like a cannonball. You exercise her constantly, but she's still hard to control. You've already taught her 'sit' and she is an expert at coming on command, but you just can't quite get her behavior under control. Training your Pit Bull puppy to lie down on command gives you a way to refocus her energy. After just a couple of weeks, you'll have her dropping her belly to the floor in a heartbeat, totally focused on you.
'Down' is one of the basic skills all puppies should learn from a young age, along with 'sit', 'stay', and 'come'. Having your puppy lie down on command is a good way to begin raising a well-behaved adult dog. It is also a building block for many other commands, including fun ones like 'bang' and 'roll over'. Most Pit Bull puppies can grasp the skill within a couple of weeks, if they already know how to sit on command.
Choose a quiet, distraction-free area in your house where your puppy can focus completely on you. You also want some high-value training treats that your puppy doesn't get at any other time. If you are doing clicker training with your puppy, it works well with this command.