just add this code in to function.php
// register add to cart action
function wnc_add_cart_button () {
add_action( 'woocommerce_after_shop_loop_item_title', 'woocommerce_template_loop_add_to_cart', 10 );
}
add_action( 'after_setup_theme', 'wnc_add_cart_button' );
There is 2 way to find out Location of function.php file
1st way – WordPress dashboard
Appearance -> Theme Editor -> function.php
2nd way – file location
wp-content -> themes -> your current theme -> function.php
