On your first visit, you will be able to access the treehouse in Nogginville. As you progress in the game, you will be able to construct and access the other areas including the Market, Theater, and Pool. If you have characters on the train and want them to join you, you can select the train icon at the bottom of the screen to access the train. To return to the Nogginville map, tap on the map icon at the top right of the screen.