I suggest you read this:
The Kennel Club | Responsible Dog Breeding
If your dog is not registered you cannot register her puppies.
The main reason for breeding is to improve the breed, not just have cute little puppies.
Breeding Yorkies is definitely not for the amateur.
I bred Lhasa's in England years ago. I had a couple of Yorkies at the time and no way would I breed Yorkies, they are more delicate than other breeds. I had my Yorkies spayed, as it was the responsible thing to do. I leave Yorkie breeding to the experts.