Changing H1 font size in Twentytwelve child theme

I am trying to change the H1 font size in my twenty twelve child theme.

I have used firebug to get the following code for the tag.

<div class="entry-content">
<h1 style="text-align: center;">
<strong>
<span style="color: #000000;"> My Text Here</span>
</strong>
</h1>

what do I put in my style sheet to change the font size?
I have tried the following

/*
 Theme Name:     twentytwelve Child Theme
 Theme URI:      ......./themes/twentytwelve
 Description:    twentytwelve child
 Author:         Me
 Author URI:     https://www.myURL.com
 Template:       twentytwelve
 Version:        1.0.0
*/

@import url("https://www.myurl.com/wp-content/themes/twentytwelve/style.css");

/* =Theme customization starts here

h1.entry-content {
	font-family: Georgia;
	font-size: 24px;
	color: #2B62AA;
}
------------------------------------------------------- */

But this didn’t work.

Can someone please tell me what I am doing wrong.

Cheers