After the completion of the first level "Follow the LEGO Brick Road", you will find yourself in a place called the Vorton Chamber.
You can replay the first level from here or enter any previously entered dimensions by stepping on the lightly glowing half of the toy pad in-game and pressing B. Select 'level select' on the far left and select any level or dimension and press A. Exit from the menus and hop through the portal. When you arrive, simply hop back through and rinse and repeat.
Alternatively, you can earn it by simply exploring all the dimensions and levels.