Change font-text size on PP

Hi

I want to change the text title and column size title on the PP. I have a child theme but adding the css to my styles folder doesn’t work. Neither does adding !important;

#front-text1 h2,
#front-text2 h2,
#front-text5 h2,
#front-columns h2 {
display: block;
float: none;
margin: 0px auto;
font-size: 20px;
line-height: 55px;
clear: both;
font-weight: 300;
}

I notice that in the Nirvana theme folder the presentation page has it’s own .css file ‘style-frontpage.css’ Do I need to make a child version of this file too?

Thanks in advance,

Kelly