How to add js to sub-menu faction for CSS styling

HI,
I am trying to figure out how I can style the sub-menu to stay up when the parent li is clicked (not only hovered). I have found a solution with JS which uses below code:

<script type="text/javascript" src="js/jquery.js"></script>
<script type="text/javascript">
        var $j = jQuery.noConflict();
        $j(document).ready(function() {
        });
        function Reveal(a){
            var ul = a.parentNode.getElementsByTagName("UL").item(0);
            $j(ul).animate({height: 'toggle' ,opacity: 'toggle'}, "slow");
        }
</script>

But I also have to add this code to the sub-menu li:
<li onclick="Reveal(this);"><a href="#">testimonials</a>

The question is I don’t know how to add onclick="Reveal(this); to the li.
Does anybody know how to add this functionality please?

Thanks,
Helen