Add this code to your child theme’s functions.php file or via a plugin that allows custom functions to be added, such as the Dessky Snippets plugin. Please don’t add custom code directly to your parent theme’s functions.php file as this will be overwritten completely when you update the theme.

/**
 * Set a minimum order amount for checkout
 */
add_action( 'woocommerce_checkout_process', 'wc_minimum_order_amount' );
add_action( 'woocommerce_before_cart' , 'wc_minimum_order_amount' );
 
function wc_minimum_order_amount() {
    // Set this variable to specify a minimum order value
    $minimum = 50;

    if ( WC()->cart->total < $minimum ) {

        if( is_cart() ) {

            wc_print_notice( 
                sprintf( 'Your current order total is %s — you must have an order with a minimum of %s to place your order ' , 
                    wc_price( WC()->cart->total ), 
                    wc_price( $minimum )
                ), 'error' 
            );

        } else {

            wc_add_notice( 
                sprintf( 'Your current order total is %s — you must have an order with a minimum of %s to place your order' , 
                    wc_price( WC()->cart->total ), 
                    wc_price( $minimum )
                ), 'error' 
            );

        }
    }
}