The menu is within the div menu-top-navigation-container
it is inheriting css from:
#access a {
color: #EEEEEE;
display: block;
line-height: 3.333em;
padding: 0 1.1em;
text-decoration: none;
}
You can find this easily by using something like firebug.
in style.css:
#access a {
color: #eee;
display: block;
line-height: 3.333em;
padding: 0 1.2125em;
text-decoration: none;
}
http://www.w3schools.com/css/css_padding.asp
also possibly:
#access div {
margin: 0 7.6%;
}
http://www.w3schools.com/css/css_margin.asp