Teaching the Settle Command
There are two parts to teaching your dog what settle means. The first part is teaching her that finding and staying on her spot is what you want, and the second part is encouraging her to lie down and relax for the duration of the settle.
Teach Your Dog to Find the Settle Spot
Start by setting up one of your dog's settle spots (for this exercise, a mat works best) before you bring your dog into the room. Put the mat anywhere on the floor you want, and put a couple of treats in the middle of it. Bring your dog into the room (no leash is necessary) and stand near the mat. As soon as your dog investigates the mat (make sure he is actually stepping on it), CR/treat, then release your dog (your stay release is fine) and pick up the mat. Put it down somewhere else in the room and put another treat on it. Again, when your dog steps on the mat, CR/treat, release, and move the mat again. Repeat until your dog is rushing to get on the mat as soon as you put it down.
Over the next several training sessions, put going to the mat on command by pointing at the mat and saying “Settle” (or “Go to bed,” or whatever you want to call it) before you let your dog step on it and CR/treat. Gradually raise your criteria so your dog has to have all four feet on the mat before CR/treating. If he steps off the mat before you release him, pick the mat up and put it down again somewhere else and work on gradually building duration in the next training sessions. When he immediately goes to the mat when you give your command and stays on it for at least 20 seconds in any position without any extra help from you, you're ready for the next step, getting comfortable.
It's Hard to Wait!
To start, make yourself comfortable in a chair or on the couch, with something to occupy your attention while you wait, like a book, the paper, or TV. Put the mat that you've been working with just to the side of where your feet will be when you're sitting. When your dog goes to check out her mat, praise her and drop a couple of treats on it. Step on the leash with both feet, giving your dog just enough room to barely stand on the mat comfortably. Have a seat yourself, and wait. Ignore anything your dog does, except when she lies down. When she does, say “Settle, good settle” and give her a couple of treats before you ignore her again. If she continues to lie down calmly, wait a few seconds, reward her again, and release her. Whether it takes twenty seconds of waiting or twenty minutes for her to lie down that first time, your dog will eventually lie down if you hang in there with her. The time that it takes for her to lie down will get shorter each time you practice, until she goes right to the mat and lies down. When that happens, have a party and quit for that session. Move to a variable reinforcement schedule as soon as she's regularly going immediately to her mat and lying down when you give her the settle command. Sometimes release her immediately; other times make her hold it for several seconds or more, gradually working her up to a minute before you reward and release.
Some dogs will not appreciate being restrained and will kick, buck, and generally throw a temper tantrum. The only thing that's important is that you keep your feet on the leash, ignore the rodeo, and wait for your dog to give up and lie down. The moment your bucking bronco hits the deck, reward and release. She'll figure out quickly that it's the calm behavior that's getting rewarded, not the wild behavior. You'll be using a couple of practical, around-the-house settle exercises to build duration and commitment even when you're not right next to her.