Step 1: Copy and paste the following HTML code in an HTML widget:

<div id="myiframe">

<p><iframe src="http://www.cnn.com"></iframe></p>

</div>

Step 2: Copy and paste the following CSS code in the theme of your community:

#myiframe iframe { width: 100%; height: 250px; border: 0 !important; }

Step 3: Adjust the red text to whatever you please

You can view a more detailed tutorial here

http://www.htmlcodetutorial.com/frames/_IFRAME.html