How do I choose which songs are used in Fitness Mode?

On the Routines tab you can toggle on and off any type of routine that you have unlocked. Strength and Cardio are always unlocked here for every song. You have to pick at least one routine type to get started. Fitness mode will use the routine types you have selected to randomly generate a playlist. We'll start by using the songs included with Dance Central Spotlight, but any new songs you buy will be added to the available list. Pick a duration, and Dance Central Spotlight will build a playlist with your songs at LEAST as long as the time you have picked. It might even go a bit over, because hey, we don't want to cut songs off in the middle.