Using the tab control in semantic-ui-open source projects Semantic-Org/Semantic-UI

I am trying to build a website using semantic-ui. I like a lot of what I see. However, I’m trying to just create a tab control. In an attempt to do this, I thought I grabbed the code found on the overview page. However, as my jsfiddle shows, the tab behavior is not working properly. Here’s a sample of my tab code:

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What am I doing wrong?