Premium users of Stages Link can use the workout builder template to create their own workouts, add them to their training calendar, and sync them with Stages Dash. Existing workouts within the workout library can also be dragged onto your training calendar and modified as needed. Once you've added the workouts to your calendar, use Stages Sync or the Stages Link app to sync them to your Dash unit.
For the Stages Dash L10, workouts can also be added via USB by saving your workout in the .FIT format and adding it to the load directory, then ejecting your Dash. The Dash will process the workout and add it to the Other Workouts location found at Main Menu > Courses & Workouts > Other Workouts.
Stages Link help:
How can I create or edit my own workout?