Okay, for example, to embed Yahoo! News, go to
https://iframely.com/domains/yahoo and grab the code there and put it into a custom box.
So, once you have the code, Go to ACP -> Configuration -> Advanced Sidebox [tab] -> Custom Boxes [subtab]
Click "Add a new custom box type"
Set the name to whatever you want.
Chang the code to this:
<tr>
<td class="trow1">
<div style="width: 98%;">
<iframe src="https://www.yahoo.com/superfan-tv/hodor-cant-hold-off-lunch-181659914.html?format=embed®ion=US&lang=en-US&site=tv&player_autoplay=false" style="border: 0; width: 100%;" allowfullscreen allow="encrypted-media"></iframe>
</div>
</td>
</tr>
NOTE: This is an example. Use this to embed whichever news feed you want.