Here is how Princess Yuna became the new princess of Skylands in Princess Yuna of Skylands.
Buzz: Boomsticks! Job Well Done, Princess Yuna!
Princess Yuna: Buzz? What're you doing here?
Buzz: Why, I've seen the whole thing what you did against Kaos, Bowser and his family. So, I've worked on a little surprise for ya.
Later, As Glumshanks and the Good Clone of Kaos led Yuna to her surprise with a blindfold on.
Glumshanks: Almost there, Princess Yuna.
Kaos (clone): And stop. Open your eyes now, Yuna.
Princess Yuna: (takes off the blindfold)
The scene revealed to be a new kingdom of Skylands.
Princess Yuna: Wow! Whose is it?
Twilight Sparkle: I believe this is your kingdom, Princess Yuna.
Inside the castle, Twilight was telling Yuna what Sharon told her.
Twilight Sparkle: Sharon told me about what you've been wondering what your kingdom should be. Now do you know?
Princess Yuna: As Princess of Skylands. It is my responsibility to watch over the Skylanders and keep the element powers within them for all times. And it took some help from my friends.
Twilight Sparkle: Then what would you do without your friends or the Skylanders? And what would Skylands be without a princess.
Princess Yuna: Wow!
The castle has an amazing throne room.
Twilight Sparkle: You are now Princess Yuna, the Princess of Skylands.
Princess Luna: (sheds a tear) We're so proud of you, Princess Yuna.
Princess Yuna: Thank you, Mama.
Dusty Crophopper: Luna. Are you crying?
Princess Luna: I'm just so happy for my little Yuna having her own kingdom.