First of all, you need to examine the google’s tool to create inserting video from youtube.

Go to developers.google.com

Then select “Youtube”.

Expand “Youtube Player Tools” and click on “Player API Demo”.

This is the Player API Tool. In the “Content:” you can enter the ID of youtube video that you want to use on your site. Also, below you could change the size of necessary video. Just enter the width and tool fits height by itself. The ID of video you could find in the “Share” tab below displayed video on the youtube site.

In the right column you need to tick “autoplay” option to allow video starts on the page opening. Also untick “control” option if you want to remove the ability to scroll the video.

Then untick “rel”, “showinfo” and “showsearch” options to remove features of the viewing video that it doesn’t need at all (like ads before and after watching).

When you do all steps, press the “Update player with selected options” button.

I strongly recommend you to use the "Object embed" tab, because not every CMS supports iframes.

Select all html code that appears in the field, and copy it (by pressing ctrl + c).

Jump to your blog’s dashboard and select the “Pages” or “Posts” to go to insert the embed html code.

Change the view mode (click on "HTML" trigger). And press Ctrl + v to paste the embed html code of the video.

Don’t forget to enter the name of page/post if you are creating new one and click on “Publish” button or "Update" in case of editing existing page/post.