To set your availability, go to Manage -->Business Settings --> Availability:
From Availability Limits, you can set availability for the entire business. If you scroll down, you can also set the availability settings for each individual package:
Video: Availability
How do I block out specific dates?
If there are specific days of the year that you would prefer not to take bookings, you can easily block those dates so that no bookings can be made for those dates. Just go to Manage --> Business Settings --> Availability --> Blockout Dates.
You can also connect your Google calendar to automatically block out any appointments that are on your calendar.
Video: Blockout Dates