Wiki TOC plugin not loading

I downloaded the Wiki TOC plugin http://expressionengine.com/downloads/details/wiki_table_of_contents/ and uploaded it to my plugins folder.

I believe that is all I should have to do and it should work. I can’t find a place to activate it. However nothing seems to be changing.

I added [TOC] and it just displays that text. I even went into the plugin and tried to echo but nothing worked there either:

$str = str_replace($this->toc_tag, "<div>{$this->marker}</div>", $str);
echo $str;
die;

So my question is do I need to do anything to activate it? If not are there any guidelines that I can use to check and see if it is actually trying to run the plugin?