As soon as the customers have the correct combination of products in the cart, the bundle discount will get applied.
However, we do have a workaround if you don't want to apply bundle discounts automatically.
You can turn off this feature in Bundler -> General settings -> Enable in online shop -> Automatically apply bundle discounts in online shop.
Your customers will then only get a bundle discount if you set the app to redirect them directly to the checkout (after they click the add to cart button in the bundle widget) OR if they accept the discount in the discount popup.
In every other case, the bundle discount won't get applied.