Go the PressTV page where they have their video and click on the icon that looks like this </> and copy the Iframe code
The Iframe code will look something like this "<iframe src="http://presstv.ir/Default/embed/420339" width="555" height="312" frameborder="0"></iframe>"
So copy that code and post it into the body of the content where you want it to show up.
And that's it
The video will show up in the post once you publish it
Here is an example