yourdomain/wp-admin/admin.php?page=wc-settings&tab=jetpack&wcj-cat=products§ion=related_products
you can set the woo related product by product categories, tag, attributes, and some options if you want to hide related products;
You can decide the quantity, columns, however, this appearance setting maybe not work to specific themes, e.g. the7 which exist related products options.
Upgrade to the paid version Booster Plus if you need to set the related products manually.
