Think of potty training your pooch the same as a child learning to crawl. You don't just let the baby have immediate freedom to roam anywhere in the house. There are too many things they could get into, even if you think you baby-proofed your house. You keep them confined with you with baby gates and playpens, and you give them things to occupy their time.
With a dog that has just entered your home, you want to do the same thing. Keep them in the room with you. If you can't watch them, put them in their crate or in an exercise pen with somethin to do. You can even leash them to your waist. If the dog has an accident in front of you; just interrupt them and take them outside. When they finish pottying in the grass treat them there. Go back in and clean up the mess with an enzyme killer (don't let your pooch watch you). If your dog goes potty and you find the mess later.... consider that your bad.
Here's the psycology part most people don't know. When you find the mess and rub the dog's nose in it, scold them, clean up the mess in front of them and shun them; this is what your dog gets out of that, "Boy, humans really get upset around pee and poo, weird. Next time I'll just hide it in the back room in the corner".
There's nothing like finding a dried pee spot behind your favorite plant in the dining room months after it has been used over and over. So the long story short is keep potty time fun, and take frequent trips to the yard. The more time you put in now, the better partner you'll have in the long run.
Happy Potty Training!!!