Core-dialog not Working

[Florence Davis]

Hi all, sorry for being a Polymer newbie here, but my core-dialog is not working I am sure if  there is something small that I am missing. 

Here is my code 

Index.html page 

<button on-tap="{{tapHandler}}">OK</button>

        <core-overlay>

          <h2>Dialog</h2>

          <input placeholder="say something..." autofocus>

          <div>I agree with this wholeheartedly.</div>

</core-overlay>

Elements Page 

<link rel="import" href="yo-list/yo-list.html">

<link rel="import" href="yo-greeting/yo-greeting.html">

<link rel="import" href="../bower_components/core-toolbar/core-toolbar.html">

<link rel="import" href="../bower_components/paper-icon-button/paper-icon-button.html">

<link rel="import" href="../bower_components/core-icons/core-icons.html">

<link rel="import" href="../bower_components/core-tooltip/core-tooltip.html">

<link rel="import" href="../bower_components/core-overlay/core-overlay.html">

<link rel="import" href="../bower_components/paper-button/paper-button.html">

[Florence Davis]

Hi guys, 

I figured it out I was missing an element.