Make sure the place is clearly defined, such as a bathroom mat. Start with your dog on a leash (you won't need a leash later on). Put a treat on the mat and make sure that he sees you doing it, but don't let him actually get the treat yet. From about 5 feet away, point at the mat, give your cue, and then run with him to the mat. Now he gets the treat he knows is there. Then give the cue for a "down-stay," and give a second treat for him complying with that. Repeat this exercise several times. Ideally he'll be running to the mat ahead of you and you'll be trailing at the end of the leash. If he's not eager to get there then you need to upgrade to tastier treats.
This will take several training sessions. Training sessions are most effective if they are short (5 minutes or so), peppy, and end on a high note. He may spend several sessions on some of the exercises. It's up to him. Go at his pace.
When you think he may have the hang of the first exercise, test by setting up as usual except don't put the treat on the mat. Fake it so that he thinks you have, but don't actually do it. When you get to the mat, be casual and see if he lies down to get the second treat for the down-stay. If he does, give him several treats in a row (called a "jackpot") and repeat this exercise several more times. If he just stares at you blankly or loses interest that's okay. It just means he isn't ready for stage two yet, so go back and repeat stage one again.
When he doesn't hesitate to lie down on reaching the mat, he's ready for stage 3. Test for this by starting off 10 feet away from the mat instead of 5 feet. For some dogs this entirely changes the game and you may have to repeat stage 1 but doing it from 10 feet away. Some dogs will be able to go right to stage 2 from 10 feet away. Let your dog decide what makes sense to him. Try different distances as you practice and run to the mat from different directions. You don't want to always have to go to the kitchen to tell him to go to his place in the living room, so practice starting toward the mat from different locations in the room.
When he's eagerly running for the mat and lying down no matter where you are in the room or how far from the mat, you can chuck the leash and continue practicing greater distances and starting from different directions in different rooms of the house. Also vary the amount of time you ask him to stay on the mat before releasing him to try the exercise again or go do something else. The rest of the training is all about building up distance and duration gradually.