How do you use iframes in your posts?

Introduction:

I'm going to talk about iframes, and how to use them in your posts. Iframes are usefull for inserting videos on your posts. When you put a link in your post you must to click on it and then a new window to youtube opens. But when you use iframes the video is already in the post, and you don't need to do anything else.

First you go to YouTube, and you choose the video you want to insert in your post. Then you click on the “Share“ button. Next to the other "share" button is the "Embed" button.