how to add paragraph on top of div content

You may use prepend to add the paragraph at the top of the container:

// HTML: <div><p>Lorem ipsum</p></div>
$('div').prepend('<p>Bla bla bla');

Update: Regarding your comment about how to fade in the paragraph – use fadeIn:

$("#pcontainer").prepend($('<p>This paragraph was added by jQuery.</p>').fadeIn('slow'));

A working demo: http://jsbin.com/uneso