Simply add the code below into your functions.php :

add_filter('woocommerce_variable_price_html', 'custom_variation_price', 10, 2);
function custom_variation_price( $price, $product ) {
$price = '';
if ( !$product->min_variation_price || $product->min_variation_price !== $product->max_variation_price ) $price .= '' . _x('From', 'min_price', 'woocommerce') . ' ';
$price .= woocommerce_price($product->min_variation_price);
return $price;
}