Welcome to YT!
Yorkies' ears are supposed to be up...that is the standard...but there are plenty of yorkies that have floppy ears. If that is the way you like them there is nothing wrong with keeping them that way.
You might not have a choice though. Their ears can be down as puppies but stand on their own or if they are large and thick they might not stand no matter what you try.
If you decide you want them to stand, keep them shaved so the weight of the hair doesn't weigh them down and you can also tape them up if it looks like they aren't going to go up on their own.
Congratulations on the new puppy!