change the size of thumbnails

-- HikaShop version -- : HikaShop Business: 2.4.0
-- Joomla version -- : 3.4.1

how do i increase the size of the extra images of the product that appear under the main image of the product when you view the individual item?

using firebug i can see to use
img.hikashop_child_image {
margin: 2px;
height: 56px;
}

but where do i put this so i can save it please?
thanks

Hello,
You'll be able to edit it through your Hikashop CSS file via "Hikahsop->System->Configuration->Display->Front-end CSS File" : www.hikashop.com/support/documentation/1...the-display.html#css