In Wordpress, how do I introduce a new div?

I'm a little confused with your question. But I will try and answer what I think your asking .

If you want to add a new div, for content such as text or images or whatever, then this is how.

html code:

<div id="newdiv"><img src="images/newimage.jpg" alt=" " /></div>

CSS code:
div#newdiv {
width:100%;
height:50px;
background:#000000;
}

This will make your div 100% the width of where it is located in. with a height of 50 pixels and a black background. You can edit your div using the CSS code the size and color etc. Also margins and paddings.

It would be helpful if we could see your site and where you wanted the div tag.

As far as the html code goes, just place it where you want the div box to be located. In your case after your navigation links and before the page content.

If you have more questions just email me.