Supervise them closely when together, and give both plenty of rest breaks to relax. Make sure the puppy is getting lots of exercise and socialization outside of playtime with your older pup. Part of growing up is learning how to behave in a polite and appropriate way with other dogs, and they learn this mostly from interacting with polite and appropriate older dogs who will (gently) show them the ropes. This shouldn't be all on your older dog--if your puppy only learns from one dog, he'll be ill-equipped to interact with all the various personalities and tolerances of the doggy world. Puppy classes can be a great way to start, and a good trainer will help you recognize good behavior and poor behavior so you know when to step in.
When you watch the interactions between the puppy and your older dog, does your older dog give consistent, gentle cues to the pup when he gets too rough or persistent? And does your puppy listen to those cues? If your older dog seems to be communicating well, I'd suggest keeping your puppy on a leash or drag line when they're together, and if the pup doesn't listen to your older dog's cues, lead him away and refocus him on another appropriate activity. Once he's behaving appropriately, release him to do what he wants, but be ready to step in again if he goes back to pestering the older dog. If your older dog is less consistent in their signals or doesn't seem to be very tolerant of the new pup, you may need to separate them more and intervene sooner to keep both of them safe and comfortable.
whenever we introduce a new family member is is gradual.I never allow anyone to fight. I have introduced dogs, cats, horse, sheep bovine etc.all this way. the trick is to never spoil one over the other, or give extra attention to the other.supervision is a must until they except each other. never ha
had an issue. We had Bonnie and Clyde when we brought home puppies Shadow and Lady, they would growl, but in time they would be ok. we had 4 dogs and 6 cats,lol. We added Ginger , when the others passed on.. we just added two cats when Missy passed on. It is rare for them to not eventually except ea
each other- just like a new family member- sometime you may have two who just do not like each other. they just may need to be separated. if you have many you introduce one by one. Most ill respect each others space.Since I was young we have done this.