** This article for stores installed app before 2024.
(discount function is already set as default mode for stores stores installed app after 2024)
* You can change app discount mode to "Discount function" in Settings > Discount. In this mode, discount codes can be applied at checkout normally.

* In other discount modes, you can enable discount code input on cart page or mini cart, then customers can apply an extra discount code right there:
https://treedify.freshdesk.com/solution/articles/43000432516-display-discount-widget-on-cart-form