How to make a discount on the main product in Woocommerce, when adding an additional one, or in a bundle?

Question

WooCommerce

How to make it so that when adding an additional item, for example, a case to a smartphone, in Woocommerce, the price of the main product changes, i.e. on a smartphone?
From what I managed to do, this is a discount on an additional product using the WPC Frequently Bought Together 1.5.6 plugin
. Also, with its help, I managed to set the total price, but the client will not understand what exactly he gets with the benefit, and we would like to focus on at a discount on the main product.
Please tell me, can anyone come across or know how to do it?
For example, a link to a product with the included plugin - https://i-ficha.ru/store/mn122/