Hello,
A new dog can be a wonderful thing for your other dog, as long as it is handled correctly. The good news is he is young enough that he will likely look at her as a companion and not competition like most older dogs would.
Since she is so young you will have to keep a close eye on them for the first week. Your male is going to want to play with her, and if you reprimand him he may feel you are picking on him so you have to handle this carefully.
When you bring her in do not hover over them, allow them both to approach each other. Do not be the new dogs crutch.....in other words sit her down and walk away. If she senses you are afraid of what may happen she is going to be fearful. If she runs to you in fear, do not pick her up. Otherwise she is going to think she has a right to be afraid. The key is to act normal and do not give her any idea that this is a scary situation.
Should your male become upset with her, then you can take him into another room or put the new dog into a new room and try again in a hour or so.
The fact is most young dogs take to new dogs easily as long as the owners do not interfere. There may be some sniffing, and maybe even some light growling which is normal.....as long as your male does not become aggressive acting there is no need to intervene. He will likely growl some over the next week or so to show the new dog he is boss. This is a normal behavior. You may want to feed them in separate bowls as well to prevent any food aggression, and always give your male his snack first. When attention is given, your male should be given the attention first, then your female.
I wish you the best with your new puppy!
Walter
Breeder
Breeder and pet health consultant. Have spent a number of years with dog rescue, training and health