You don't.
you go to nuvema town to your house and talk to looker
After you have Looker arrest the last sage out of the Seven Sages, He should thank you and he should also tell about a boy who sounds exactly like N, who has been seen with a dragon pokemon somewhere far away... ^_^
Continue your journey :]
Yo mammas house
Looker goes away after you find the Seven Sages.
looker only comes when you beat the game and he gives you a Super Rod and you meet him when you find the seven sages.
Looker says good work and there's been a sighting of an N-ish person in a nearby city that he's gonna check out
You have to find the seven sages well 6 as looker arrests one when u catch reshirim or zekrom
I think he disappears and you don't see him anymore
He says he is going to a distant place to look for a legendary pokemon, but he doesn't give you anything.
Once you have found the Seven Sages the looker will tell you that he saw N but he let him go. You can not find N in the actual game play.
no one knows exactly where but their was a report that he is at a far away place. at the end and your in your room come down stairs and you will find out.