Well if she is only 1 year old she is too young. Usually you wait until the dog is on her third heat to ensure she has matured enough to be able to handle carrying and delivering and nursing a litter.
That also gives you time to check for knee, hip, skin, or eye problems and get her certified with CERF and OFA etc and to make sure her color is correct.
You should study up on what might go wrong and be ready to pay for a c-section if she needs one etc.
Dogs can only breed during the female's heat season and will only mate when the female is ready to ovulate. Usually the heat is 3 weeks long and breeding normally happens between days 9-14 but dogs vary and may breed earlier or later than that by a little.
You might find this site and their breeding tips useful
http://www.yorkie.org/
Hope this helps you!

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