Increase the space between main picture and thumbnails below it

Hi guys,

May I know how to increase the gap between the thumbnails and the main picture on top of them ? As now on my page, the thumbnails is inline with the main picture.

Here is the URL of my store: http://www.normanaudio.com/store/tonik/

Thanks,
Phong

https://wordpress.org/plugins/woocommerce/