I Think this will do either in Your style.css, Custom CSS or Child Theme – style.css:
.sidebar h3 {
background: url("images/sprite_master.png") no-repeat scroll -390px top transparent;
clear: both;
color: #333232;
font: bold 13px/33px "Trebuchet MS";
height: 33px;
letter-spacing: 0.03em;
margin: 0 0 5px -12px;
padding-left: 12px;
width: 243px;
}
The font line: font: bold 13px/33px "Trebuchet MS";
is where You can choose the font size or font You like best 🙂
You find style.css here:
http://cappiesallinone.com/wp-admin/theme-editor.php
Kim