To embed stories inside articles go to My stories page, click the Embed option on the right-side panel. Select the <iframe> embed type - the code will get copied automatically:
Sample code:
<iframe src="https://stories.nws.ai/1288000000/test/?opts=fb:1" frameborder="0" scrolling="no" style="width:300px;height:600px;position:relative;margin:0 auto;display:block;"></iframe>