footer and CSS

-- HikaShop version -- : 4.0.1
-- Joomla version -- : 3.8.2
-- PHP version -- : 5
-- Browser(s) name and version -- : firefox

Hi,
I would like to know that can I add the images and text in the position of footer,
the same position (or higher) of " HikaShop , Joomla!® E-Commerce Extension".
the second thing is my Hikashop version is 4.0.1
in this version, where can I open the CSS to parameter my site ?
because I found everywhere, and I didn't find out the CSS file.
I wish someone can help me.
thank !