Centrer le texte du menu du thème simone (Créer un compte)

Bonjour,

Ma configuration WP actuelle
– Version de WordPress : 4.1
– Version de PHP/MySQL : php5.5 mysql5.6
– Thème utilisé : Simone
– Extensions en place : wp-rocket / wp sitemap
– Nom de l’hebergeur : f3re
– Adresse du site : http://www.toevenstay.com

Problème(s) rencontré(s) :
Impossible de centrer le menu du theme !

Voici le fichier css (seulement pour la navigation)

/*

---

5.2 Main Menu

---

*/
.main-navigation {
position: relative;
display: block;
width: 100%;
clear: both;
font-family: ‘Lato’, sans-serif;
text-transform: uppercase;
background: #313131;
background: hsl(0, 0%, 19%);
}

.main-navigation ul {
margin: 0;
padding-left: 0;
list-style: none;
}

.main-navigation li {
position: relative;
float: left;
}

.main-navigation a {
display: block;
padding: 1.3em 1em;
font-size: 14px;
font-size: 1.4rem;
text-decoration: none;
line-height: 1.3em;
color: white;
color: hsl(0, 0%, 100%);
}

.main-navigation ul ul {
position: absolute;
left: 0;
z-index: 99999;
display: none;
float: left;
padding: 0;
background: #4d4d4d;
background: hsl(0, 0%, 30%);
}

.main-navigation ul ul ul {
top: 0;
left: 100%;
}

.main-navigation ul ul a { width: 200px; }

.main-navigation ul ul li { }

.main-navigation li:hover > a,
.main-navigation li > a:focus {
color: #fff;
color: hsl(0, 0%, 100%);
background: #4d4d4d;
background: hsl(0, 0%, 30%);
}

.main-navigation ul ul :hover > a { }

.main-navigation ul ul a:hover,
.main-navigation ul ul a:focus {
background: #313131;
background: hsl(0, 0%, 19%);
}

.main-navigation ul li:hover > ul { display: block; }

.main-navigation .current_page_item > a,
.main-navigation .current-menu-item > a,
.main-navigation .current_page_item > a:hover,
.main-navigation .current-menu-item > a:hover,
.main-navigation .current_page_item > a:focus,
.main-navigation .current-menu-item > a:focus {
color: #313131;
color: hsl(0, 0%, 19%);
background: white;
}

.main-navigation .current_page_ancestor {
background: #4d4d4d;
background: hsl(0, 0%, 30%);
}

.main-navigation ul ul .current_page_parent,
.main-navigation .current_page_parent .current_page_item > a {
color: #fff;
color: hsl(0, 0%, 100%);
background: #313131;
background: hsl(0, 0%, 19%);
}

/* Small menu */
.menu-toggle {
display: none;
cursor: pointer;
}

@media screen and (max-width: 600px) {
.menu-toggle {
display: inline-block;
height: 3.9em;
padding: 0 1em;
font-weight: normal;
font-size: 14px;
font-size: 1.4rem;
text-decoration: none;
line-height: 3.75em;
color: white;
}

.menu-toggle a:hover,
.menu-toggle a:focus {
background: #4d4d4d;
background: hsl(0, 0%, 30%);
}

.main-navigation.toggled .nav-menu {
display: block;
border-top: 1px solid;
border-top-color: #fff;
border-top-color: hsla(0, 0%, 100%, .5);
}

.main-navigation ul {
display: none;
padding-left: 0;
}

.main-navigation li { float: none; }

.main-navigation li a { padding: 1.3em 2em; }

.main-navigation li li a { padding-left: 4em; }

.main-navigation li li li a { padding-left: 6em; }

.main-navigation li:hover > a,
.main-navigation li > a:focus {
background: #313131;
background: hsl(0, 0%, 19%);
}

.main-navigation ul ul,
.main-navigation ul ul ul {
position: relative;
top: inherit;
left: 0;
display: block;
float: none;
background: #313131;
background: hsl(0, 0%, 19%);
}

.main-navigation ul ul a { width: 100%; }

.main-navigation ul a:hover,
.main-navigation ul ul a:hover,
.main-navigation ul a:focus,
.main-navigation ul ul a:focus{
background: #4d4d4d;
background: hsl(0, 0%, 30%);
}

.main-navigation .current_page_ancestor { background: inherit; }

.main-navigation ul ul .current_page_parent {
color: inherit;
background: inherit;
}

.main-navigation .current_page_item > a,
.main-navigation .current_page_item > a:hover,
.main-navigation .current_page_item li:hover,
.main-navigation .current_page_item > a:focus,
.main-navigation .current_page_item li:focus,
.main-navigation .current_page_parent .current_page_item > a {
color: #fff;
color: hsl(0, 0%, 100%);
background: #4d4d4d;
background: hsl(0, 0%, 30%);
}

} /* End responsive menu */