To insert a Youtube video pass the following steps:
Open a youtube page.
Click on the Share link
Select Use old embed code
Specify your size and copy the embed code above
Go to your store admin panel, open the Content section, select an article (or add a new one)
In the editor toolbar, click on the HTML icon
Paste the code and save the changes
If you want to display it on your index page go to the Page Manager,
select index.php and add a block. Paste the code to the block content or
use this tag:
<?php CMSPageContent('your_article_id'); ?>
where your_article_id is the id of the article created in the Content section.