The "down" command is a basic obedience command in dog training. Before teaching your dog to lie down on command, they must have already mastered the "sit" command.

• Ask your dog to sit.
• Grab a treat, and let your dog see that you have the treat.
• Slowly lower the treat to the floor in front of your dog, moving your hand further away from your dog as you get closer to the floor.
• As your dog follows the treat, they will lower their body.
• When their elbows touch the floor, click or mark, and then reward your dog.
• After your dog masters the basics of this command, gradually make it more challenging by adding some variations.

With consistent practice, your dog will learn to associate the "down" command with lying down on cue. Remember to be patient and use positive reinforcement while training your dog. Good luck!