The Monstars are on Tour, so clicking the Tour button will bring up Tour Map.
On the Tour Map you can see all of the cities that are on this Tour and the order in which you will visit each city. Clicking the city will take you to the level map for that city. There are 25 shows (levels) that you must complete to be able to move on to the next city. The music stand next to each city shows the number of notes that you have collected from all of the shows in that city. There is a maximum of 75 notes per city.
Once a city is unlocked, you can move to that city by simply clicking on it. When you do that it will move your tour bus to that city.