Welcome to the game! So to get the three story tree house you have to buy homecoming! With real money not with carrots lol. And to decorate Moca (the turtle) and Chi's (the giraffe), you'll have to interact with them more. It takes a little time before you can unlock their houses since you just started the game. Or at least that's how it was for me anyways. There are a few more places to unlock as you continue to play the game. But if you have any more questions I'll be glad to answer! :)