Changing size of Font in Checkout

-- HikaShop version -- : 2.4.0
-- Joomla version -- : 3.3.6
-- Browser(s) name and version -- : Firefox 37.0.1

I'm sorry to have to ask the question but I have tried to change the front end CSS to make the text larger in the checkout log in and checkout forms without any success. Am I right to be adding it to the end of the CSS box. The CSS I am using is <style>
{
font:16px verdana;
}

If I find out how/where this is done I would also like to change the colour the font.

I appreciate any help.