I agree with illusive. You really should separate them for quarantine reasons..it would be awful if Nugget caught some kind of illness from Pineapple. It can take quite some time for a hidden illness to show up but it can still be passed on to your Nugget. They should be quarantined from each other in separate rooms. This will help not only to prevent passing illness, but also with training
It will also be much much easier to bond with and train your new guy/gal if he's not in with another bird. If he has another bird with him, he will undoubtedly bond with another bird before a human.
No mirrors in the new one's cage as it may bond with the bird in the mirror not with you.
S/He needs time and patience...lots n lots of patience.. to learn that he can trust you.
I also think it is unfair to Nugget to have another bird forced upon him, invading HIS home and territory without so much as even getting to know it first. Heck Nugget may not even LIKE the new kid. They don't all like each other. Just like people...we like some, and some we just plain don't.
It will, like illusive mentioned, take time, until your new one is at least 8 mos old to determine whether you have another male there, or if it's a female.
If female you would want to keep them separate or you will have breeding issues and babies to deal with. Having babies is really hard on a female, it can be dangerous, and you really have to do tons of research and learn a LOT to know what to do before even considering it. There's a lot to breeding if you want to keep your female safe and in good health.
Are you even sure that Nugget is a male? You say "he" when referring to him.
And what makes you think Pineapple is a girl?
Sooo....separate them and take time to sloooowly bond with Pineapple before even considering caging them together.
Start by doing exactly what illusive suggested
Oh btw..welcome to the forum.
Looking forward to seeing pics of your bird kids and hearing more about how training goes with Pineapple