Help website crashed

I was adding plugin to my site and when I added W3 Total Cache or Super Cache I got this message Fatal error: Call to undefined function shopp() in /home/nataliea/public_html/wp-content/plugins/shopp-cache-helper/shopp-cache-helper.php on line 77 Now what do I do to fix this? I’m really new at all this and am not technical at all. I don’t understand at all how to fix this, so I need detailed how to. I’m sorry.