You can add opening hours easily by going to Settings> Channel Settings. The Channel Settings are only visible to a user with Manager rights. At the top you must first select a channel. You can then set the opening hours of that channel at the bottom of the page.
Do you have custom closing days or closing times you’d like to set for the holidays?
You can also set this. By adding custom closing days. You first choose a day and then the times. By adding custom closing days, you send customers an out-of-office message when your business is closed.