Inside your jCarouselLite div, you should add your navigation buttons just like the js source file shows. Then tell the script where to locate the buttons.
In other words modify the pageload script like this:
$(".jCarouselLite").jCarouselLite({
auto: 3000,
speed: 600,
btnNext: ".next",
btnPrev: ".prev"
});
And inside your container div add the buttons:
<div style="visibility: visible;" class="jCarouselLite">
...
<button class="prev"><<</button>
<button class="next">>></button>
</div>
Of cours you're free to throw away <button> for the html element of your choice like a div, span etc.
The important this is to insure that the elements declared in your script have the same class or id as those in your html markup.