Now that you've brought him home, here are some basic tips to stop him soiling your house.
1. When inside, closely supervise your dog. If can't be with him, confine him to a small area or exercise pen during house training. Continue this until he has gone at least 4-8 weeks without any accidents.
2. Always accompany him outside to eliminate.
3. Take him out frequently, especially after eating, sleeping, and play activities.
4. Immediately reward outdoor elimination with praise and treats. Do it as soon as he has finished. (If you wait until back inside, he will think the reward is for coming back inside.) Consider keeping a jar of treats near the door as a reminder to take a few on your way outside.
5. Provide an area for elimination that is protected from rain and bad weather.
6. If you catch him eliminating inside, startle him with a loud noise and immediately take him outside to finish eliminating. Then, once again, reward your dog immediately.
7. Clean soiled inside areas with enzymatic cleaners. These can be purchased at pet supply stores. You need to eliminate the smell so he doesn't associate indoors with elimination.
8. Don't punish when he slips up. This is rarely effective. Instead reward good behaviour.
Seriously consider puppy school and obedience classes. They will help teach him basic commands and that you are the alpha, or top, dog in the household. They also provide positive interaction between you and your dog. Trainers of these classes can be an invaluable source of information for housebreaking and other behaviour modifications. Your veterinarian may be able to recommend a behaviourist in your area. Be sure to choose someone who uses reward- or clicker-based training.