Add and showcase the needed upsell products, which would be interesting for customers, who purchase the product shown on Single Product page, in a special section
Favorites are a Member’s Only feature, which you can access right now for FREE simply by creating your own account.
It’s that simple.
Did you see the other "WooCommerce : Upsells" addons like the
WooCommerce : Single Upsells?
p.s. You can find these under the "More Like This" section on each widget/extension page :)