Fatal error with install of wp shopping cart 3.6.8 rc2

First I am not a web designer or code saavy, can’t get the person who made my site to help, so I am learning VERY slowly and painfully on my own, was having trouble with the shopping cart and saw there was an upgrade available, so out of frustration decided to try to upgrade, watched video et al on how to and thought I did it but……7 hrs later…….would appreciate help….
Fatal error: Call to undefined function: wp_enqueue_style() in /nfs/c01/h07/mnt/36747/domains/nativeorleanian.com/html/news/wp-content/plugins/wp-shopping-cart/wp-shopping-cart.php on line 2906…

this is the error