The iFrame object specifies an inline frame. An inline frame is used to embed an external content within the current App.
So you can use it to display a web page within the App, including embeddable content like those offered from YouTube, Twitter, Google Maps and other online services.
This object corresponds to the <iframe> HTML tag.
Edit the source property on the Properties Panel to specify the URL where the content is hosted.
For example, copy and paste this URL on the source property: https://www.youtube.com/embed/pa14VNsdSYM
It is necessary test the App to actually see the content inside the iFrame object, so click on the Run botton or on any of the Browsers buttons to test it.
You should see and embedded videoclip from YouTube.