You can make changes to your schedule directly from the "Manage Schedule" section of your app. The courier app allows you to schedule yourself up to 7 days in advance. Add yourself to any available one-hour time slot by pressing it. Press again to take yourself off. The current day is always locked, so you won't be able to change your schedule for that day.
You are not required to add yourself to a schedule, but if you do, we ask that you do your best to schedule only when you intend to work.