Click the "Create New Schedule" button:
Name your schedule (perhaps according to the time of day). Choose a playlist from the dropdown list:
Now you have a wide range of choices for how to schedule. Note that the "From" field is a dropdown that can be changed to "All Day" when you don't need this schedule to alternate with others.
It's also important to note the Day dropdown offers quite a few choices to have certain schedules on certain days without complicated timing:
Mondays, Tuesdays, Wednesdays, Thursdays, Fridays, Saturdays, Weekdays, Weekends