Answer: Because Kreature did what Harry told him to do. Did you mean " how did Sirius know that Harry inherited Grimmauld Place"? because Dumbledore didn't know for sure.
Answer: I guess he just read the will of the last Black heir (Sirius Black).
Harry Potter inherited it from Sirius Black.
He inherits Sirius Black's house - Grimmauld Place and his house elf, Kreacher.
12 Grimmauld Place
Sirius's house, Grimmauld Place.
7 is a magical number in Harry Potter. There are 7 Harry Potter books. Also, wizards are considered adults when they are 17. Number 4 Private Drive is Harry's address for most of the books. 12 Grimmauld place is Harry's inherited house.
You meant where they met? In HP5, they met at Number twelve , Grimmauld Place , which is the Black's house for generations. In HP6 , there was nothing about the Order but Harry (who recently inherited Grimmauld Place from Sirius) insisted that it was kept as Headquaters. In HP7 , Number twelve , Grimmauld Place was Headquaters. But when Hermione gave the secert to Yaxely , it wasn't Headquaters anymore. The Burrow was. But when Lord Voldemort took over the Ministry , Shell Cottage , where Bill and Fleur lived , became Headquaters ever since.
9 people
Number 12, Grimmauld Place
Dumbledore is neither a real nor a fictional place. It's the name of a Harry Potter character.
He lives in number 12, Grimmauld Place with the Order of the Phoenix
Kreacher brought Mundungus to Grimmauld Place.
That depends on which house you're talking about. Bill is Secret Keeper for Shell Cottage. Dumbledore is secret keeper for 12 Grimmauld Place.