Show CSS menu item selected by default using Jquery

I have created a menu bar using CSS and HTML. Menu bar contains sub-menu as well.

I am able show menu-item on hover of main menu item etc. But now I need Menu Item 2 (or one menu item), to be hovered/selected by default, (as soon as the page loads) and its related sub-menu items to be shown by default as well. Please guide me through the same.

I have tried adding a class on the first item using Jquery :

$(document).ready(function(){
  $("get the id of the menu item").click(function(){
       $(this).parent().find("id of the menu item").addClass('class to be added');   
  }); //but what should be written in the class so that menu item is active and its sub menu items are shown by default

});

HTML Code :

<ul id="menu-main" class="menu"><li id="menu-item-24" class="menu-item menu-item-type-custom menu-item-object-custom current-menu-item current_page_item menu-item-home menu-item-24"><a href="#">Test1</a></li>
  <li id="menu-item-25" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-has-children menu-item-25"><a href="#">Test2</a>
<ul class="sub-menu">
 <li id="menu-item-267" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-267"><a href="#">Sub Menu1</a></li>
</ul>
</li>
<li id="menu-item-27" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-has-children menu-item-27"><a href="#">Test3</a>
<ul class="sub-menu">
<li id="menu-item-33" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-33"><a href="#">S1</a></li>
<li id="menu-item-34" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-34"><a href="#">S2</a></li>
<li id="menu-item-30" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-30"><a href="#">S3</a></li>
<li id="menu-item-278" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-278"><a href="#">S4</a></li>
<li id="menu-item-281" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-281"><a href="#">S5</a></li>
</ul>
</li>
<li id="menu-item-31" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-31"><a href="#">Test4</a></li>
<li id="menu-item-258" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-258"><a href="#">Test5</a></li>
<li id="menu-item-253" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-253"><a href="#">Test6</a></li>
</ul>

And the CSS :

ul.sub-menu{position:relative;
z-index:40;}
ul#menu-main ul {
display: none;
}

ul#menu-main li:hover > ul {
display: block;background-color: red;
} ul#menu-main {



position: relative;
display:inline-table;
top: 42px;
position: relative;
float:right;
margin-bottom: 0px;
clear: both;
padding: 0 0 0 20px;
background: transparent!important;
list-style: none;
height: 60px;
font-family: BebasNeueRegular, Helvetica, Arial Narrow, sans-serif;
font-size: 18px;
}
 ul#menu-main:after {
 content: ""; clear: both; display: block;
}
ul#menu-main li {
float: left;
line-height: 60px;
z-index: 40;
margin-left: 15px;
}

 ul#menu-main li a:hover {
    color: #fff;
background: #f29919;

}
ul#menu-main ul li{ border-bottom:1px solid #eee;}
ul#menu-main ul li a:hover {
color: #818181;
background: #eee;

}


ul#menu-main li a {
display: block;
font-family: BebasNeueRegular, Helvetica, Arial Narrow, sans-serif;
padding: 0 20px;
color: #818181;
text-decoration: none;
}
ul#menu-main ul {
border-radius: 0px; padding: 0;
position: absolute; top: 100%;
}
ul#menu-main ul li {
float: none; 

position: relative;
list-style:none;
/*width: 180px;*/
line-height: 37px;
margin-left: 0px;
}ul#menu-main ul li:first-child{border-top: 1px solid white;}

ul#menu-main ul ul li a:hover {
color:white;
}

ul#menu-main ul ul {
position: absolute; left: 100%; top:-1px;
}
ul#menu-main li.current-menu-item > a{
color: #fff;
}


ul#menu-main ul ul li:hover a{
color: #333333;
}