After her coronation Twilight went back to Ponyville to pick up her things from her previous home: the library.
Of course Spike didn't want to leave because of Rarity so Twilight let him and Owl-wishes stay at the library in Ponyville.
The girls grouped hugged and she returned to Canterlot.
The two princess sister showed Twilight her wing of the castle.
It has a large room connected to the Canterlot Arkives and had a view of Ponyville when going out on her balcony.
Twilight put her stuff down and started to arrange everything when Celestia and Luna had to lower the sun and raise the moon respectively so they had to leave Twilight for a while alone.
The first thing she does is take out her sacred diary opens the magical lock and starts to write.