Hi there,
You can insert your custom social media links in unused social media slots. For example, if you don’t use Pinterest, you can insert your ACF link there and change the icon by using CSS. The CSS code that you need to add in the Customizer > Custom > CSS is
.x-social-global .x-social-pinterest:before {
content: url("Add image URL here");
}
The code should be added under Customize -> Custom -> CSS.
Hope it helps.