Very good advice.I add a little more to Corteo:
1. Make sure that you clean up the yard very well.
2. Take a small bit of poop and place it where you want them to go.
3. Not necessary, but it might be easier if you separate each dog's area by about 5 feet.
4. Keep the area cleaned up at least twice a week.
One other thing. I notice that my dog does NOT pee and poop in the same place.... so I let him pee outside where he wants.