Change Font of Sub Menu

Hi, I’m a newbie to WP and I’m trying to change the font size of sub items in a form. I’ve searched solutions in the forums and seen multiple threads with solutions that have worked for people. Here are the ones I’ve tried without success in my Update Custom CSS (see below…)

Like I say, none of these have worked. Any suggestions?

.sf-menu ul li a {
font-size: 1.2em !important;
}

#main-navigation .sub-menu li {
font-size: 1.3em !important;
}

#top-navigation .sub-menu li {
font-size: 1.3em !important;
}

#nav-second ul.sf-menu ul li a {
font-size: 12px;
}

#submenu a {
color: #FFFFFF;
font-size: 150%;
font-weight: bold;
padding: 3px 5px 3px 7px;
text-shadow: 0 1px 0 #555555;
}