The Online Order app will use the Business Hours set in your Clover Setup app. If your Business Hours are already set, then you simply click on the "Sync Hours" button found in the Pickup Hours box.
If you have not set your Business Hours, you can click on the "Open POS" button found in the Pickup hours box. This will open the Clover Setup app where you set your Business Hours. The Business Hours are found in the Business Information tab, of the Clover Setup app. You will have to scroll towards the bottom to see the Business Hours fields.
Once your hours are set correctly in the Clover Setup app, remember to click "Sync Hours" button found in the Pickup Hours box.
If your working hours are past midnight, remember that you will need to take the hours of the next day as necessary for that shift, you can have this complex set up as long as your workings hours are not overlapping. e.g. For a shift on Friday night from 08:00 pm to Saturday 02:00 am, I will have to set two working days : Friday from 8 PM to 12:00 midnight, and Saturday from 12:00 midnight (AM) to 2 AM.