The store opening hours dictate the times when bookings can be made in both the backoffice and online. If you would like the online booking hours to differ from the backoffice opening hours, see setting online booking hours.
To set your store opening hours visit settings -> opening hours.
When you visit that page you will be shown a 'blank page' of hours.
You can enter some hours and press bulk set to set them all.
Then you can adjust each days' opening hours, or set any day(s) to closed.