In the discount page, click on add a discount.
Choose to apply the discount automatically. Make sure to navigate through the conditions and validity tabs to configure your discount settings.
After saving the discount, guests will automatically receive the discount in their bookings.
In the example below, the booking has a total amount of 560€ and the automatic discount was set to 100€:
After finishing the booking, the discount is applied and booking has the total amount of 460€ (100€ was discounted):