Press Z or tap the screen to see another level. To add to new levels, remix the project and use the level template. Make sure to include information on entities found in there, how to enter the level, and your scratch name in the corner (For credit purposes) Your Dankrooms levels will then be seen and possibly added to the main project (If this happens then it's canon)
The music in the background is the Mii channel music! The name of the creator of a level is in the bottom left corner. This is to make it easier to know who created which level.