Hi,
You can do that by modifying the code in the file "show_default" via the menu Display->Views.
You simply have to move the block of code displaying the description
<div id="hikashop_product_description_main" class="hikashop_product_description_main">
<?php
echo JHTML::_('content.prepare',preg_replace('#<hr *id="system-readmore" */>#i','',$this->element->product_description));
?>
</div>
where you need it.
I suppose that you meant above the "add to cart" button, and not above the shopping cart, since there is no shopping cart been displayed in the product page layout. In that case, you should put the description code before the line
<div id="hikashop_product_quantity_main" class="hikashop_product_quantity_main">