Adding a puppy to a home with another dog, or, in my case, 5 other dogs is usually much easier than bringing in an older dog. That's too bad, because I believe in adoption and rescue only.
I just brought a young dog home to my pack 2 weeks ago. He is a big puppy at about 3 or 4 months of age. I was very careful with his initial introduction, and i've let the dogs teach him the dog pack rules, and I've done the normal obedience training: sit, down, come, stay.
The other and maybe most important thing is to thoroughly socialize the puppy to anything he might encounter later, like riding in a car, an elevator, meeting people on the street, traffic noise. Anything you can think of.
Your "only dog" is going to have some adjustment issues. They may be very minor or could escalate. I believe it is very important to allow the older dog to assert a fair degree of dominance - but the key is FAIR.
My method is very simple. When I hand out treats, by 6 dogs need to sit quietly and take turns AND, I am the one who determines the order of the who gets fed first, second and so forth. I deliberately randomize it to reinforce my absolute discretion to the dogs.
At the end of the day, you will get the dog you deserve, meaning that most dogs will pay attention only to those things you really care about enought to train them to do. If you don't care about dogs on the couch, you probably aren't going to be consistent enough with your training to have a dog that doesn't get on the couch. And so forth.
A new puppy is a lot of work, and it takes patience and understanding to raise a really healthy, happy, social and responsible dog citizen.