Yorkie pups began eating on their own at about 6 weeks. They need to be about 12 weeks old before they are old enough to eat dry food and be placed in their new home. Many breeders of pet Yorkies will sell their pups before this time. I would caution you not to take your new pup home until a minimum of 12 weeks. During this time they learn many things from their dam and litter mates such as bite inhabition and how to respond to other dogs.
By 12 weeks old, they should be eating dry food. If you like, you can add a little canned food if need be to make sure they eat well when being in a new environment.
Some pups may be afraid at first and may need some encouragement to eat. Things you can try in feeding them are cottage cheese mixed with their food or maybe a small pice of cheese. Too much canned dog food can give them an upset stomach and cause loose stools. The main thing is to be sure they eat so as not to become hypoglycemic.
Most Yorkies don’t like a lot of hard treats. There are small biscuits they can eat. Keep treats to a minimum as they will not eat their food if given too many. Treats have a lot of salt and sugar in them. People food should not be fed to any dog. Small carrots, apples, and other veggies are ok. No starchy or fatty foods.
A high quality food should be fed. Please do not feed Old Roy or any similar brands. Yorkies eat a small amount so a good quality food should be used. I would caution you from feeding any treats that are produced in China.