In each product from, you can enter a discount price.
In 'Settings/Sales period', you can select three dates:
In 'Settings/Happy hour', you can select the start time and end time of the Happy Hour period.
To apply the discount prices to a sale, click on the 'Discount prices' button (or 'Happy Hour' button) in the right side of the sale (this button is displayed only during the sale event / Happy hour).
In 'Settings/Users/Access management', enable the right 'Apply discount prices automatically in Sales period or Happy Hour time', to apply automatically the discount prices when products are added to the sale.