1) As mentioned earlier, but worth repeating, do not connect the inner canine seat buckle to your Yorkie's collar. With any sort of impact, this can cause terrible neck injuries or even death. The connector is meant to be clipped to your dog's
harness
(even if the photo on the product does not show this).
2) The safest spot to place the car seat is in the middle of the back seat. Understandably, many owners want their Yorkie up in front with them.
If you opt to do that, it is recommended that you move the passenger seat as far back as it can go and that you disable any passenger air bags. Air bag deployment can cause serious injury to death both to small dogs and children.
3) If your Yorkie is fussy
about being in the car (and the car seat will indeed help with that for most puppies and dogs), you may want to reserve some fun toys only to be given when in the car. Just this alone can make a dog look forward to car trips.
Please take the same safety precautions with your Yorkie that you would with a baby. Your dog depends on you to make the right choices and take all steps to keep him safe.