If possible weather permitting I like to introduce the new dog to the current ones on more neutral ground. On leads even if it is just outside the front door on the sidewalk. Then take both for a wee walk. Five or ten minutes or so.
Then still on lead we enter the house, the current dogs first, and I will crate the current dogs. The puppy is then let off lead to "investigate" this new house - its smells and rooms. Well at least the two rooms it will be in until housebroken. Their xpen with bed and the Blankie from the breeder is set up and then the pup goes in the xpen. Although usually after the excitement of exploring, they need to wee again, so out we go to the backyard - on lead to where I'd like the pup to eliminate. My dogs are crated in the same room, and that is where I set up the temporary Xpen.
Then in comes pup and into Xpen with a treat and a toy. Other dogs are released from their crate, and we all settle in the same room, watch TV or I read.
You may find housebreaking a snap cause you already have a dog that can show the other the "way".
Once all the dogs have slept and ate together, walked and been groomed, etc you will probably find that everyone gets along quite well. You are building your pack!
Now if your current dog is not well socialized to other dogs, that is something you can work on now. Invite a friend over to go for a walk with their dog and yours. Have a cup of tea afterwards with the dogs in your home. See how your boy behaves himself.
Note on Toys: I don't leave out toys. Toys are special rewards that they get for doing some obedience/training work. Toys come out when we play the game of "find the toy". Then the toys go away. Each crate has a "stuffless toy" in it that they can chew on, and be undisturbed by their brother or sister.
Very High Value Treats: Here I am very cautious. I do feed once a week real bones. I never leave the dogs unattended when they are contentedly knawing away. I had one gal that always lost interest early in hers, and would like to go over and sniff/smell the other dogs bones. This I discouraged and she was crated until the other dogs finished theirs. I always pick up the bones once they are done and put them immediately into a secure garbage bin.
Feeding: Separate bowls in separate areas of the kitchen. I always stay right in the kitchen until the pups are done eating. They know not to go over to the others bowl until everyone is done; but still I supervise. It is a real hoot to watch the three or four dogs, go over to check out each others' empty bowls
I also put down fresh water for everyone, but an interesting tidbit in our home, is that all the other dogs want to drink out of our Alpha male's bowl. They ignore their water, wait until he is done, then each one goes over to lap up on his water.
Maybe it is shades of in the wild the Alpha's eat and water first, then the rest of the pack.
I think you will get to enjoy a Little Pack. Life changes a lot for everyone.
Good luck in your search